Add test coverage against go tip

[h9jiang]

vscode-go's integration test (including the npm test) is running against the last released go version. Before go1.24 is released, the test use 1.23. So vscode-go does not have test coverage against go version other than the last released version including the gotip.

In vscode-go, some code lenses or code actions are executing go command to achieve some behavior like go test, go mod tidy and the test is written based on the last released version of go when writing the test. If go changes the behavior in the next release, the test will fail.

It's natural that go may change it's behavior to have stricter rules or improved results so vscode-go should evolve with go at the same time. However, what is not desirable is the timing. The vscode-go test start failing after the go1.24 release because go vet behavior change. And vscode-go itself is preparing for it's next minor version v0.46.0.

We should introduce a test coverage against go tip so we dont get this surprise behavior during vscode-go release.

With the help of migration to LUCI, LUCI will prepare different go versions in different builders. And vscode-go need to copy the go binary, compiler, toolchain and standard library from the builder to docker image so the go version inside of docker is the same as the go version in LUCI builder.