mktemp: strict type and allow #run without chdir

[cho-m]

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Was looking into #18548 and thought we could avoid some duplication by adjusting Mktemp.

In this case, the other PR would use

Mktemp.new("homebrew-unpack").run(chdir: false) do |tmp_unpack_dir|
  tmp_unpack_dir = T.must(tmp_unpack_dir.tmpdir)

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This PR does restrict arguments for Mktemp so no longer an accept an arbitrary hash but instead takes in specific boolean parameters.

I think this is fine as it is a private API, but can restore opts if preferred.

[MikeMcQuaid]

Looks great thanks @cho-m!