Separate Bitbucket Server Importers Logic - Part 2

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What does this MR do and why?

See full context in !149302

This is Part 2 from a series of MRs to handle issues: #451129.

• Part 1 - Moving HTTP calls

• Part 2 - Separate Importers Logic <-- This MR

• Part 3 - Add Paging on HTTP Calls

• This MR is under feature flag development, intended to be opened after the series of MRs are completed.

• The main changes are separating importer classes and changing the parameter from "object" style to "hash" style:

  • Merge event from PullRequestNotesImporter to PullRequestNotes::MergeEvent
  • Approved event from PullRequestNotesImporter to PullRequestNotes::ApprovedEvent
  • Inline comments from PullRequestNotesImporter to PullRequestNotes::Inline
  • Standalone PR comments from PullRequestNotesImporter to PullRequestNotes::StandaloneNotes

• Previous changes on PullRequestNotesImporter are reverted in favor of the new PullRequestNoteImporter. Which is called by a new worker Gitlab::BitbucketServerImport::ImportPullRequestNoteWorker

MR acceptance checklist

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Before	After
	MR List:
	Approved Event:
	Standalone Comments:
	Inline Comments:
	Merge Event:
	New Importer Class:

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Initial environment setup can follow this
2. Prepare some data in Bitbucket Server
3. Patch the code to inject interruption:

diff --git a/gems/gitlab-http/lib/gitlab/http_v2/url_blocker.rb b/gems/gitlab-http/lib/gitlab/http_v2/url_blocker.rb
index 99876c779539..06bd0c6b92cd 100644
--- a/gems/gitlab-http/lib/gitlab/http_v2/url_blocker.rb
+++ b/gems/gitlab-http/lib/gitlab/http_v2/url_blocker.rb
@@ -64,6 +64,9 @@ def validate_url_with_proxy!(
         )
           # rubocop:enable Metrics/ParameterLists
 
+          allow_localhost = true
+          allow_local_network = true
+
           return Result.new(nil, nil, true) if url.nil?
 
           raise ArgumentError, 'The schemes is a required argument' if schemes.blank?

4. Tail the log file: tail -f log/importer.log
5. Go to http://127.0.0.1:3000/import/bitbucket_server/status
6. Click Import