Made state-level failhard override global failhard.

[github-abcde]

Also update documentation for failhard and onfail-requisites.
(I hope I got the refs right)

What does this PR do?

It allows a global failhard setting to be overriden by a state-level failhard setting.

What issues does this PR fix or reference?

#20496

Previous Behavior

Whenever global failhard is True, even setting failhard to False in the state still causes the state run to be aborted.

New Behavior

A state-level failhard setting of False overrides (for that state only) a global failhard.

Tests written?

No

Commits signed with GPG?

Yes

[thatch45]

Just make sure that this is never backported into a point release because this is a behavior change :)

[rallytime]

@github-abcde Can you add a mention of this to the Fluorine release notes, please?

[github-abcde]

@rallytime This is new to me. Does this mean I have to add an entry to `docs/topics/releases/fluorine.rst'? (And would that be including the mention not to backport it?)

[rallytime]

@github-abcde Yeah, sorry for being unclear there. We need to make sure that behavior changes of this kind are documented in the release notes. In this case, that means the Fluorine.rst file. You don't need to worry about mentioning not to back-port this in the release notes.

[rallytime]

@garethgreenaway Can you review this again, now that some doc updates have been added?

[rallytime]

@github-abcde Ah, there looks to be a merge conflict in the release notes. Can you rebase this and fix the conflicts? Thanks!

[github-abcde]

@rallytime Done