Fix windowsPath to handle local named pipes correctly

What does this MR do?

• Fixes windowsPath.IsRoot and windowsPath.IsAbs to correctly handle Windows local named pipes, and adds tests.
• Fixes a minor bug in the windowsPipe regex in executors/docker/internal/volumes/parser/windows_parser.go which would also match \\a\pipe\namedpipe.
• Adds a test to executors/docker/internal/volumes/manager.go to use the Windows path class (all the rest are using the Unix version).
• Renames addParser to addUnixParser to make it clear which parser implementation we're using in a given test.

Why was this MR needed?

See #4295 (closed)

What's the best way to test this MR?

Unit tests

Check that the unit tests are passing and test the intended scenarios.

Before the fix to the code:

$ vagrant up && vagrant ssh
vagrant@VAGRANT-2019 C:\Users\vagrant>cd %RUNNER_SRC%
vagrant@VAGRANT-2019 C:\GitLab-Runner>go test -run TestWindowsIsAbs .\helpers\path
--- FAIL: TestWindowsIsAbs (0.00s)
    --- FAIL: TestWindowsIsAbs/named_pipe_path (0.00s)
        windows_path_test.go:90:
                Error Trace:    windows_path_test.go:90
                Error:          Not equal:
                                expected: true
                                actual  : false
                Test:           TestWindowsIsAbs/named_pipe_path
    --- FAIL: TestWindowsIsAbs/named_pipe_path_with_forward_slashes (0.00s)
        windows_path_test.go:90:
                Error Trace:    windows_path_test.go:90
                Error:          Not equal:
                                expected: true
                                actual  : false
                Test:           TestWindowsIsAbs/named_pipe_path_with_forward_slashes
FAIL
FAIL    gitlab.com/gitlab-org/gitlab-runner/helpers/path        0.027s
FAIL

vagrant@VAGRANT-2019 C:\GitLab-Runner>go test -run TestWindowsIsRoot .\helpers\path
ok      gitlab.com/gitlab-org/gitlab-runner/helpers/path        0.033s

vagrant@VAGRANT-2019 C:\GitLab-Runner>go test -v -run TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows .\executors\docker\internal\volumes
=== RUN   TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows 
=== RUN   TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows/pipe_name_volume_specified 
panic:

mock: Unexpected Method Call
-----------------------------

VolumeCreate(*context.emptyCtx,volume.VolumeCreateBody)
                0: (*context.emptyCtx)(0xc000030118)
                1: volume.VolumeCreateBody{Driver:"", DriverOpts:map[string]string(nil), Labels:map[string]string{"com.gitlab.gitlab-runner.job.before_sha":"", "com.gitlab.gitlab-runner.job.id":"0", "com.gitlab.gitla
b-runner.job.ref":"", "com.gitlab.gitlab-runner.job.sha":"", "com.gitlab.gitlab-runner.pipeline.id":"", "com.gitlab.gitlab-runner.project.id":"0", "com.gitlab.gitlab-runner.runner.id":"", "com.gitlab.gitlab-runner.runner.local_id":"0", "com.gitlab.gitlab-runner.type":"cache"}, Name:"uniq-cache-2be4e73b4826f26a0049c7794d38cdb0"}

After the fix to the code:

vagrant@VAGRANT-2019 C:\GitLab-Runner>go test -run TestWindowsIsAbs .\helpers\path
ok      gitlab.com/gitlab-org/gitlab-runner/helpers/path        (cached)

vagrant@VAGRANT-2019 C:\GitLab-Runner>go test -v -run TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows .\executors\docker\internal\volumes

vagrant@VAGRANT-2019 C:\GitLab-Runner>go test -run TestWindowsIsRoot .\helpers\path
ok      gitlab.com/gitlab-org/gitlab-runner/helpers/path        (cached)

vagrant@VAGRANT-2019 C:\GitLab-Runner>go test -v -run TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows .\executors\docker\internal\volumes
=== RUN   TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows
=== RUN   TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows/pipe_name_volume_specified
=== RUN   TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows/duplicate_pipe_name_volume_specified
--- PASS: TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows (0.00s)
    --- PASS: TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows/pipe_name_volume_specified (0.00s)
        manager_windows_test.go:62: PASS:       VolumeCreate(string,mock.argumentMatcher)
        manager_windows_test.go:63: PASS:       Path()
        manager_windows_test.go:63: PASS:       ParseVolume(string)
        manager_windows_test.go:63: PASS:       ParseVolume(string)
    --- PASS: TestDefaultManager_CreateUserVolumes_CacheVolume_VolumeBased_Windows/duplicate_pipe_name_volume_specified (0.00s)
        manager_windows_test.go:63: PASS:       Path()
        manager_windows_test.go:63: PASS:       ParseVolume(string)
        manager_windows_test.go:63: PASS:       ParseVolume(string)
PASS
ok      gitlab.com/gitlab-org/gitlab-runner/executors/docker/internal/volumes   (cached)

Manual tests

1. Set up a Windows VM with Docker:

   vagrant up --provider virtualbox 2019-box

2. Copy the fixed Windows Runner .exe to a directory in the VM using the VirtualBox File Manager.

3. Register the runner:

   gitlab-runner-windows-amd64.exe register -c .\config.toml -n -u https://gitlab.com/ -r <registration token> --tag-list "windows,docker,vagrant" --executor docker-windows --docker-image mcr.microsoft.com/windows/servercore:ltsc2019 --docker-helper-image gitlab/gitlab-runner-helper:x86_64-575a5585-servercore1809 --docker-volumes "c:\cache" --docker-volumes "\\.\pipe\docker_engine:\\.\pipe\docker_engine"

4. Start the runner:

   gitlab-runner-windows-amd64.exe run -c .\config.toml

5. Run any build against it. A failed build (using a master branch build) is shown here. The same job was replayed against the branch runner and succeeded.

What are the relevant issue numbers?

Closes #4295 (closed)