cask: add pwsh_completion stanza - #24046

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The cask DSL was missing a pwsh_completion stanza; this adds it to better align it with the formula DSL.

I would also like to propose reordering the existing shell completion stanzas to:

bash_completion
zsh_completion
fish_completion

Homebrew's documentation uses this order in multiple places, e.g. Shell Completions generate_completions_from_executable. There is no enforced sort order on formulae, but from what I've seen, most sort them like this already.

This would affect 9 casks. This PR includes a workaround for the sort cop so that we can transition them to the proposed order.