chore: fix changelog format, update preset, and improve release action

[dbudzins]

Description

This PR updates the github release actions.

First, the create release action is updated to use CHANGELOG as an input file, which preserves the existing content and appends just the new release, instead of regenerating the whole file each time. It also changes the preset to conventionalcommits because the angular preset uses h1 headings in markdown for some versions instead of always using h2 which breaks tools like changelog readers.

Accordingly, I manually updated the changelog to fix all of the h1 headings to be h2.

Lastly, I updated the release and tag action to read the current version and changelog changes from package.json and CHANGELOG.md respectively, instead of trying to rerun the changelog generator. This prevents the version from double incrementing and also means when you commit to the release branch, the release details created matches what you see in the release candidate branch.

Steps completed:

According to our definition of done, I have completed the following steps:

~- [ ] Acceptance criteria met~ ~- [ ] Unit tests added~

• [x] Docs updated (including config and env variables) ~- [ ] Translations added~ ~- [ ] UX tested~
• [x] Browsers / platforms tested
• [x] Rebased & ready to merge without conflicts
• [x] Reviewed own code

[github-actions[bot]]

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