chore: miscellaneous repository maintenance

[x] Closes #1172
[x] Fixes broken links on markdown files.
[x] Add missing changelog entry from #1160
[x] Rename makefile to Makefile.
[x] Remove unnecessary nix use in cw-check.
[x] Remove rokroskar/workflow-run-cleanup-action from Rust workflow over native concurrency support.
[ ] ~Setup merge_group with correct workflow status checks.~
- [x] Disable merge_group trigger.
- [x] Always run important workflows on main.
- [x] Remove markdown link checks from main.
[x] Use ~.yml over .yaml~ .yaml over .yml as workflow file extensions.
[x] Use actions-rust-lang/setup-rust-toolchain.
[x] Update download artifact example for Tendermint wasm client.

Setting up merge_group is a bit complicated. To auto-remove a PR from merge_group, we need to add them as status_check for merges onto main. But if a job is not executed (because of filtering of paths or trigger events), it will never be added in merge_group - because we need all status checks to be passed before merge.

The merge_group only works for a workflow something as following:

name: Status Check Jobs
on:
  pull_request:
  merge_group:
    types: [checks_requested]

jobs:
  my-job:
    if: ${{ github.event_name != 'pull_request' }}
    steps:
      run: echo "Hello World"

So the workflow is marked as successfully executed on PR, albeit it didn't run any job. When, the PR is put in merge_group, it will actually run my-job.

PR author checklist:

[ ] Added changelog entry, using unclog.
[ ] Added tests.
[ ] Linked to GitHub issue.
[ ] Updated code comments and documentation (e.g., docs/).
[ ] Tagged one reviewer who will be the one responsible for shepherding this PR.

Reviewer checklist:

[ ] Reviewed Files changed in the GitHub PR explorer.
[ ] Manually tested (in case integration/unit/mock tests are absent).

cosmos / ibc-rs

chore: miscellaneous repository maintenance #1174

PR author checklist:

Reviewer checklist:

Codecov Report