[flutter_tools] add --verbose flag to pub global activate

[christopherfujino]

try to debug #82142

[flutter-dashboard]

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[Hixie]

test-exempt: is a test

[christopherfujino]

Landing this without the Mac module_custom_host_app_name_test check as this PR should not affect that test (it is flaking on master), and this PR will help us diagnose a separate flake.