Add in Test Flags for improved test results based on factors

Closes #200 (closed) Related #201 (closed)

MR adds in the concept of flags tags to tests. flags can be used to specify additional info about tests. In this MR one flag is added, repo_storage that signifies the test is for an endpoint that is affected by repository storage type (gitaly or nfs) and will adjust test thresholds accordingly.

Several improvements and additions were made to support the above. Also adjusts thresholds for several tests based on new results from customers.