refactor: make GHPullRequestReviewComment extend GHIssueComment

[Anonycoders]

Description

• Depends on fix: GHPullRequestReviewComment.getLine() returning -1 #2188 - rebase after the merge.
• Fixes GHPullRequestReviewComment should extend GHIssueComment #2013

• Refactors GHPullRequestReviewComment to properly extend GHIssueComment, following the same inheritance pattern as GHPullRequest extends GHIssue
• Adds bodyHtml and bodyText fields to GHIssueComment per GitHub Issue Comments API
• Implements Refreshable interface on GHPullRequestReviewComment

Before submitting a PR:

• Changes must not break binary backwards compatibility. If you are unclear on how to make the change you think is needed while maintaining backward compatibility, CONTRIBUTING.md for details.
• Add JavaDocs and other comments explaining the behavior.
• When adding or updating methods that fetch entities, add @link JavaDoc entries to the relevant documentation on https://docs.github.com/en/rest .
• Add tests that cover any added or changed code. This generally requires capturing snapshot test data. See CONTRIBUTING.md for details.
• Run mvn -D enable-ci clean install site "-Dsurefire.argLine=--add-opens java.base/java.net=ALL-UNNAMED" locally. If this command doesn't succeed, your change will not pass CI.
• Push your changes to a branch other than main. You will create your PR from that branch.

When creating a PR:

• Fill in the "Description" above with clear summary of the changes. This includes:
  • If this PR fixes one or more issues, include "Fixes #" lines for each issue.
  • Provide links to relevant documentation on https://docs.github.com/en/rest where possible. If not including links, explain why not.
• All lines of new code should be covered by tests as reported by code coverage. Any lines that are not covered must have PR comments explaining why they cannot be covered. For example, "Reaching this particular exception is hard and is not a particular common scenario."
• Enable "Allow edits from maintainers".

[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.11%. Comparing base (3ecd46e) to head (b52ffbc).

Files with missing lines	Patch %	Lines
...org/kohsuke/github/GHPullRequestReviewComment.java	60.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2189      +/-   ##
============================================
- Coverage     85.14%   85.11%   -0.04%     
+ Complexity     2525     2522       -3     
============================================
  Files           239      239              
  Lines          7461     7457       -4     
  Branches        393      393              
============================================
- Hits           6353     6347       -6     
- Misses          872      874       +2     
  Partials        236      236              

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