replace atom in utils.rb with vscodium

[earthsound]

Verification

• This issue's title and/or description do not reference a single formula e.g. brew install wget. If they do, open an issue at https://github.com/Homebrew/homebrew-core/issues/new/choose instead.

Provide a detailed description of the proposed feature

Currently, atom is first in the list when searching for editors in utils.rb.

# Find Atom, Sublime Text, VS Code, Textmate, BBEdit, or vim
    editor = %w[atom subl code mate bbedit vim].find do |candidate|
      candidate if which(candidate, ORIGINAL_PATHS)
    end

Since atom is deprecated and (at least on my MPB) marked as harmful (iirc due to code signature expiration) could we replace atom with codium?

What is the motivation for the feature?

Atom is deprecated and something needs to replace it.

How will the feature be relevant to at least 90% of Homebrew users?

Going with the spirit of the discussion in #2915 (pointing out why atom was added as the first option), replacing atom with an open source GUI editor seems to make the most since. VS Code is further down in the list (code), but I'm making the assumption I'm not the only one who prefers VSCodium.

What alternatives to the feature have been considered?

None.