🌱 Add tagsHandler to githubrepo client

[AdamKorcz]

What kind of change does this PR introduce?

This adds a tagsHandler to the githubrepo client. The tagsHandler follows a similar procedure as the branchesHandler and reuses many of its utilities. The tagsHandler implements the following methods:

1. init: Similar to branchesHandler's init.
2. setup: Fetches all rulesets and tags of the repository and stores it.
3. query: Returns a clients.RepoRef of a branch.
4. getTags: Returns a slice of all tags as RepoRef's with their rulesets.
5. getTag: Calls query and returns the RepoRef.

To implement this tagsHandler, I have had to make a number of changes:

1. I have renamed BranchRef to RepoRef.
2. I have renamed branch ref.
3. I have renamed other similar types from being branch-specific to be logically usable for storing tag data.

Furthermore, I have added GetTag and ListTags methods to the repoclient interface and the clients that implement the repoclient. This is the most user-exposed the tagsHandler currently, and these two methods are not used anywhere. They are there to demonstrate the intent of how to use the githubrepo tagsHandler.

The PR is quite large as it is now, so I'd prefer to follow up with probes for this once it is merged.

(Is it a bug fix, feature, docs update, something else?)

• PR title follows the guidelines defined in our pull request documentation

What is the current behavior?

What is the new behavior (if this is a feature change)?**

• Tests for the changes have been added (for bug fixes/features)

Which issue(s) this PR fixes

Fixes #10 and #2476

Special notes for your reviewer

Does this PR introduce a user-facing change?

For user-facing changes, please add a concise, human-readable release note to
the release-note

(In particular, describe what changes users might need to make in their
application as a result of this pull request.)

NONE

[codecov]

Codecov Report

❌ Patch coverage is 59.82533% with 92 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.22%. Comparing base (353ed60) to head (fea6945).
⚠️ Report is 228 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4770      +/-   ##
==========================================
+ Coverage   66.80%   68.22%   +1.42%     
==========================================
  Files         230      251      +21     
  Lines       16602    19076    +2474     
==========================================
+ Hits        11091    13015    +1924     
- Misses       4808     5191     +383     
- Partials      703      870     +167     

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[github-actions]

This pull request has been marked stale because it has been open for 10 days with no activity