[YAML] - Normalize YAML PubSub format

[ffernandez92]

addresses #31067

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[brucearctor]

Lgtm. will leave open a couple days for anyone to comment, though should be fine to merge

[robertwb]

Are there any examples we need to update?

[brucearctor]

@ffernandez92 -- once you've confirmed docs/website/etc updated [ if necessary ], we can merge.

@robertwb -- should we also update syntax/style guide? That seems outside scope of this PR, but perhaps worth specifying to further specify desired conventions.

[ffernandez92]

@brucearctor, I've updated the docs, website, and tests [I didn't see specific examples to fix] to ensure they are consistent with the new uppercase scenario. They currently function regardless of whether it's upper or lower case. However, I'd like to be prepared for when we deprecate the lowercase option so that we don't need to modify the tests.
As you've said, we can leave the PR open for a couple of days in case there is more feedback