Regression tests

items to test

• pin down issues related to proc-macro-nested causing issues for wasm32 builds on Windows platform.
• fix the current snapshot & integration tests in CI. May need to scrap them for something which will not break related to hashing of content.
• CI cache is giving very strange errors as well, let's fix that up. Currently, cache code is commented.
• ensure index.html file is served as a fallback.
• test the proxy system with an echo server to ensure requests are proxied and echoed back.
• test the trunk config show command output with some snapshot tests to ensure Trunk.toml and env vars are processed properly.
• snapshot test --help output to ensure we don't hit a regression in CLI help output.