context: prefer pre-computed CgoContextInfo from go_context_data (#4591)

Reorder the CgoContextInfo resolution in go_context() so that the
pre-computed value from go_context_data is checked before falling back
to cgo_context_data_impl().

This avoids re-running the expensive cgo_context_data_impl for every
go_library target when a shared CgoContextInfo is already available from
the cgo_context_data rule.

Perf improvements:
| | Before | After |
|--|--|--|
| `cgo_context_data_impl` CPU | 132s | **0.02s** |