go_path: Support embedsrcs of generated files

[S-Chan]

What version of rules_go are you using?

v0.34.0

What version of gazelle are you using?

v0.24.0

What version of Bazel are you using?

Bazelisk version: development
Build label: 5.1.0
Build target: bazel-out/darwin-opt/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar
Build time: Thu Mar 24 14:10:21 2022 (1648131021)
Build timestamp: 1648131021
Build timestamp as int: 1648131021

Does this issue reproduce with the latest releases of all the above?

Yes.

What operating system and processor architecture are you using?

Darwin x86_64

Any other potentially useful information about your toolchain?

What did you do?

Added a Go library that uses go:embed as a dependency to a go_path rule. The go:embed file was generated with a copy_file rule.

What did you expect to see?

Files embedded in Go library to be copied into the generated GOPATH.

What did you see instead?

fail("Path '%s' is not beneath '%s'" % (path, start))
Error in fail: Path 'bazel-out/k8-fastbuild/bin/foo/bar' is not beneath 'foo'

Exact filenames edited

[S-Chan]

This is an enhancement of #3162