Consider using executable_search_path in go backend

[henri14]

The Problem
Whilst working on #21292 I noticed that the go backend uses separate options for search paths. These are _go_search_paths and _cgo_tool_search_paths. I needed an additional search path for the extra-tools option but ended up implicitly using the _go_search_paths.
A number of other backends seem to use executable_search_path option. These are Docker, NodeJS, Pex and Shell.

The Proposal
Enhance the go backend to use executable_search_path for the go binaries, cgo tools and extra tools. This would be done by using the ExecutableSearchPathsOptionMixin.
This would improve consistency in the options for the various backends. It does however impact existing configs that would need to be migrated.