Split git tag and github release options

[bluwy]

fix #247
fix #547

NOTE: the above issues requested documentation improvements, but I have not done them here yet. I think probably it's easiest to consolidate all the docs update once we've finished reworking the actions & sub-actions.

Possible alternatives

1. I wonder if it should be push-git-tags instead of create-git-tags, because we'd actually only do the pushing. (renamed)

1. This is a breaking change because create-github-releases: false previously also disabled push tags, but now it'd push by default, unless set push-git-tags: true explicitly.

   We can kinda prevent this breaking change by making push-git-tags always follow the value of create-github-releases, unless push-git-tags was explicitly set, but I feel it's a bit hard to follow compared to the current behaviour, where both are independent options, just that create-github-releases: true will always force push-git-tags: true because inherently that's how github releases work.

   Or we support some sort of create-github-releases: "tag-only" but this also seems a bit weird.

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Latest commit: 39422af

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[trueberryless]

Amazing. Changes look good to me, the logic seems fine. Description matches the behaviour.

Do we have any tests yet for the actions?

[bluwy]

Our tests currently is very loose. We should get to that after we're finished with most of the big changes I think.