ACD changelog generator

[felixfontein]

Current output: https://gist.github.com/felixfontein/7d5efcc70c8a25c218d9e8082f5ee92f

Doesn't yet contain ansible-base's changelog.

(I've added a 2.10.0a2 release with the latest collection versions, as otherwise there are no changelogs at all.)

[felixfontein]

Generated with:

antsibull-build build-changelog 2.10.0a2 --deps-dir ../ansible-build-data/2.10 --collection-cache cache

(2.10.0a2 was created with time antsibull-build build-single 2.10.0a2 --collection-cache cache --build-file ../ansible-build-data/2.10/acd-2.10.build --deps-file ../../ansible-build-data/2.10/acd-2.10.0a2.deps --dest-dir built)

[felixfontein]

I've implemented some changes in antsibull-changelog's changelog generation code to allow improving the porting guide (see ansible-community/antsibull-changelog#24).

[felixfontein]

(Probably breaks in CI until antsibull-changelog gets another release.)

[felixfontein]

(antsibull-changelog 0.5.0 has been released with the required changes.)

[felixfontein]

Trying out a new style:

• before: https://gist.github.com/felixfontein/7d5efcc70c8a25c218d9e8082f5ee92f#file-changelog-v2-10-style-1-rst
• after: https://gist.github.com/felixfontein/7d5efcc70c8a25c218d9e8082f5ee92f#file-changelog-v2-10-style-2-rst
• porting guide: https://gist.github.com/felixfontein/7d5efcc70c8a25c218d9e8082f5ee92f#file-porting_guide_2-10-rst

[abadger]

Not a request to change this code necessarily; when I wrote the type checking for DependencyFileData.__init__() I wondered if I should make it t.Union[str, Version] (where Version was either packaging Version or semantic version... I don't recall off the top of my head which one it is).

If you think it's more convenient to change the DependencyFileData API (now or in the future), that would be fine with me.

[abadger]

This looks good to me. Merge when you're ready.