Upgrade to Crystal v0.30.0

[bcardiff]

(and formatter)

A bump of optarg with mosop/optarg#7 should be included in the next release.

[bcardiff]

Note that there is a spec failing since 0.28.0. I didn't dig deeper into that. The CI is a bit outdated and the issue wasn't noticed up until today AFAIK.

$ crystal spec spec/internal/explicit_exit_calls_standard_exit_spec.cr:4 
F

Failures:

  1) CliInternalExplicitExitCallsStandardExitFeature
     Failure/Error: {{ run("#{__DIR__}/explicit_exit_calls_standard_exit/run").stringify }}.should eq ":) 99\n"

       Expected: ":) 99\n"
            got: ""

     # spec/internal/explicit_exit_calls_standard_exit_spec.cr:5

Finished in 120 microseconds
1 examples, 1 failures, 0 errors, 0 pending

Failed examples:

crystal spec spec/internal/explicit_exit_calls_standard_exit_spec.cr:4 # CliInternalExplicitExitCallsStandardExitFeature