feat(changelogs): Add github-changelog and gitlab-changelog hosttypes

[rv2673]

Changes:

Behaviour changes

• Make it possible to apply hostRules to changelog lookups.

Code changes

• Introduce hostTypes for gitlab and github changelog lookups, so (specific) hostRules can be applied.
• Add those types to the existing hostRule fallback mechanism for gitlab and github respectively

Context:

• Closes Differing behaviour retrieving gitlab-tags and releases between datasource and changelog #13497

• Replaces fix(gitlab): Consistent urlencoding and call source specific hostType for gitlab (changelogs, packages, tags, releases)  #13577(Same but with url encoding seperated out to different request, see discussions there) and fix(gitlab): Consistent urlencoding and call source specific hostType for gitlab (changelogs, packages, tags, releases)  #13577

• This PR should probably be merged after refactor(gitlab-changelog): Make url encoding consistent #13694

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please tick one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[viceice]

needs deconflicting

[rarkins]

I don't like this, but it solves the problem and we don't have a better solution for now

[renovate-release]

🎉 This PR is included in version 31.66.0 🎉

The release is available on:

• GitHub release
• 31.66.0

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