Servicing docs improvements

[carlossanlop]

Adding more details to our servicing documentation, particularly around the check-servicing-labels CI leg.

Starting with the 7.0-staging branch to confirm the CI workflow changes work, then will backport to 7.0, 6.0-staging, 6.0, and finally to main.

Also want to confirm if:

• An "echo" message can show the link to a md file properly.
• The PR template can link to the current branch's doc, instead of the main doc.

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Issue Details

---

Adding more details to our servicing documentation, particularly around the check-servicing-labels CI leg.

Starting with the 7.0-staging branch to confirm the CI workflow changes work, then will backport to 7.0, 6.0-staging, 6.0, and finally to main.

Also want to confirm if:

• An "echo" message can show the link to a md file properly.
• The PR template can link to the current branch's doc, instead of the main doc.

Author:	carlossanlop
Assignees:	carlossanlop
Labels:	documentation, area-Infrastructure
Milestone:	-

[hoyosjs]

/backport to main

[github-actions]

Started backporting to main: https://github.com/dotnet/runtime/actions/runs/4898788375

[hoyosjs]

/backport to release/6.0-staging

[github-actions]

Started backporting to release/6.0-staging: https://github.com/dotnet/runtime/actions/runs/4898789433

[github-actions]

@hoyosjs backporting to release/6.0-staging failed, the patch most likely resulted in conflicts:

$ git am --3way --ignore-whitespace --keep-non-patch changes.patch

Applying: Servicing docs improvements
Using index info to reconstruct a base tree...
M	.github/PULL_REQUEST_TEMPLATE/servicing_pull_request_template.md
M	docs/project/library-servicing.md
Falling back to patching base and 3-way merge...
Auto-merging docs/project/library-servicing.md
Auto-merging .github/PULL_REQUEST_TEMPLATE/servicing_pull_request_template.md
CONFLICT (content): Merge conflict in .github/PULL_REQUEST_TEMPLATE/servicing_pull_request_template.md
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Servicing docs improvements
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

[github-actions]

@hoyosjs an error occurred while backporting to release/6.0-staging, please check the run log for details!

Error: git am failed, most likely due to a merge conflict.

[carlossanlop]

@hoyosjs thanks for trying, but backport can't be easily done with these changes. I'll submit the rest of the PRs manually.