[Dev] Update GitHub Actions workflows that hardcode master as default

[asfimport]

git rev-parse --abbrev-ref origin/HEAD | sed s@origin/@@ will tell us what the default branch is. Identify the default branch and use it.

• https://github.com/apache/arrow/blob/master/.github/workflows/archery.yml#L52
• https://github.com/apache/arrow/blob/master/.github/workflows/comment_bot.yml
• Update https://github.com/apache/arrow/blob/master/ci/detect-changes.py#L231 to be master or main; also update comments

Reporter: Neal Richardson / @nealrichardson
Assignee: Neal Richardson / @nealrichardson

PRs and other links:

• GitHub Pull Request #12436

_{Note: This issue was originally created as ARROW-15690. Please see the migration documentation for further details.}

[asfimport]

Krisztian Szucs / @kszucs:
Issue resolved by pull request 12436
#12436