Original issue: https://github.com/rust-lang/rust/issues/21195
Relevant PR: https://github.com/rust-lang/rust/pull/30778
Prior to this commit, if a compiletest testcase included the text
"HELP:" or "NOTE:" (note the colons), then it would indicate to the
compiletest suite that we should verify "help" and "note" expected
messages.
This commit updates this check to also check "HELP" and "NOTE" (not the
absense of colons) so that we always verify "help" and "note" expected
messages.
As part of the audit for #22820 the following feature gate tests have
been added:
* `negate_unsigned`
* `on_unimplemented`
* `optin_builtin_traits`
* `plugin`
* `rustc_attrs`
* `slice_patterns`
