Display old and new version numbers when updating Homebrew

[apainintheneck]

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This outputs the old and new version numbers along with the version hashes when they are different otherwise it outputs the old message. This was first proposed in issue #12760.

$ brew update    
Updated Homebrew from 3.3.9 (db648bcde) to 3.3.11 (249b0439e).
...
==> Homebrew was updated to version 3.3.11
The changelog can be found at:
  https://github.com/Homebrew/brew/releases/tag/3.3.11

Closes #12760

[MikeMcQuaid]

Thanks so much for your first contribution to Homebrew/brew! Without people like you submitting PRs we couldn't run this project. You rock, @apainintheneck!