No longer omit stdlib dependencies from dependency inference.

Omitting these packages would break backport libraries (such as dataclasses). Performance impact is negligible since the dependency graph has already been gathered.

Benchmarks using `$ hyperfine --warmup=1 --runs=10 './pants --no-remote-cache-{read,write} --no-pantsd dependencies ::'`
Before these changes (omitting stdlib dependencies):
```bash
Benchmark pantsbuild#1: ./pants --no-remote-cache-{read,write} --no-pantsd dependencies ::
  Time (mean ± σ):      8.852 s ±  0.105 s    [User: 8.612 s, System: 5.314 s]
  Range (min … max):    8.702 s …  9.107 s    10 runs
```

After changes (with stdlib dependency inference)
```bash
Benchmark pantsbuild#1: ./pants --no-remote-cache-{read,write} --no-pantsd dependencies ::
  Time (mean ± σ):      8.854 s ±  0.123 s    [User: 8.619 s, System: 5.333 s]
  Range (min … max):    8.682 s …  9.111 s    10 runs
```

[ci skip-rust]
[ci skip-build-wheels]