Update changelog validation scripts to match MetaMask/core

[Mrtenz]

In an effort to standardise the repository more, I'm working on matching different parts of our repository configuration to match MetaMask/core. In this PR I've updated our changelog validation scripts, and formatted the changelogs using Prettier.

This also solves a long standing issue where we would have to format changelogs each time after creating a new release PR.

There are a lot of changes in this PR, but the notable changes are in the package.json files:

• lint:changelog is now changelog:validate.
• changelog:validate now accepts a --fix parameter which will be properly forwarded to the validation script.
• There is a new changelog:update script.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.35%. Comparing base (e3cbd4a) to head (9f49669).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2741   +/-   ##
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  Coverage   94.35%   94.35%           
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  Files         476      476           
  Lines       10137    10137           
  Branches     1542     1542           
=======================================
  Hits         9565     9565           
  Misses        572      572           

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