CI: Remove unnecessary test-functionality test wrappers (#1393)

CI: Remove unnecessary test-functionality test wrappers (#1393)

These workarounds are not needed for the current and future code in this
branch. Other branches get their own test-functionality.sh files that
can be used to maintain a branch-specific collection of test wrappers.

The (now unused) has_commit_by_message() function was left in the script
because that function is likely to be used by future workarounds. Unlike
specific test workarounds that only apply to a subset of old code, this
and similar functions can be viewed as a reusable code "library".