Proxy fix

[badsyntax]

Refs #397

• Disable http proxy in the gRPC client
• Remove race condition workaround if gRPC server is slow to start
• Proxy tests

[badsyntax]

Tests successfully failing here: https://github.com/badsyntax/vscode-gradle/runs/737513604?check_suite_focus=true (odd that tests only fail in windows. they fail locally for me on macos, perhaps it's a github actions VM thing)

And tests successfully passing here, showing the http proxy fix in grpc-js works: https://github.com/badsyntax/vscode-gradle/actions/runs/124539042

[sonarqubecloud]

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[badsyntax]

Tests are now failing and succeeding as expected. LGTM.