Improve performance of fetching build/bzl files for a project
Improve performance of fetching build/bzl files for a project

```
buildfiles(deps($T1)+deps($T2)+deps($T3)+[...])
```

is equivalent to, but generally much slower than

```
buildfiles(deps($T1+$T2+$T3+[...]))
```

PiperOrigin-RevId: 389912462
(cherry picked from commit a5ef86ecdd7d0946eb2f3f87f8d392ed080d35e3)

bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi