Fix isolation groups for unused imports

[charliermarsh]

Summary

The isolation group for unused imports was relying on checker.semantic().current_statement(), which isn't valid for that rule, since it runs over the scope, not the statement. Instead, we need to lookup the isolation group based on the NodeId of the statement.

Our tests didn't catch this, because we mostly have cases that look like this:

if TYPE_CHECKING:
    import shelve
    import importlib

In this case, the two fixes to remove the two unused imports are considered overlapping (since we delete the full line, and the two full lines touch, and we consider exactly-adjacent fixes to be overlapping), and so they don't run in a single pass due to the non-overlapping-fixes requirement. That is: the isolation groups aren't required for this case. They are, however, required for cases like:

if TYPE_CHECKING:
    import shelve

    import importlib

...where the fixes don't overlap.

Closes #6758.

Test Plan

cargo test

[github-actions]

PR Check Results

Ecosystem

✅ ecosystem check detected no changes.

Benchmark

Linux

group                                      main                                   pr
-----                                      ----                                   --
formatter/large/dataset.py                 1.00      3.8±0.07ms    10.8 MB/sec    1.06      4.0±0.04ms    10.2 MB/sec
formatter/numpy/ctypeslib.py               1.00   790.6±20.60µs    21.1 MB/sec    1.07    843.7±8.85µs    19.7 MB/sec
formatter/numpy/globals.py                 1.00     83.2±2.61µs    35.5 MB/sec    1.08     90.0±1.19µs    32.8 MB/sec
formatter/pydantic/types.py                1.00  1559.7±29.68µs    16.4 MB/sec    1.05  1642.3±16.37µs    15.5 MB/sec
linter/all-rules/large/dataset.py          1.00     11.5±0.17ms     3.5 MB/sec    1.02     11.7±0.14ms     3.5 MB/sec
linter/all-rules/numpy/ctypeslib.py        1.00      3.2±0.07ms     5.3 MB/sec    1.02      3.2±0.04ms     5.2 MB/sec
linter/all-rules/numpy/globals.py          1.00    463.1±4.70µs     6.4 MB/sec    1.00    462.1±6.15µs     6.4 MB/sec
linter/all-rules/pydantic/types.py         1.02      6.2±0.10ms     4.1 MB/sec    1.00      6.1±0.08ms     4.2 MB/sec
linter/default-rules/large/dataset.py      1.00      6.3±0.07ms     6.5 MB/sec    1.00      6.3±0.12ms     6.5 MB/sec
linter/default-rules/numpy/ctypeslib.py    1.00  1371.4±42.69µs    12.1 MB/sec    1.02  1402.2±18.21µs    11.9 MB/sec
linter/default-rules/numpy/globals.py      1.00    155.5±3.01µs    19.0 MB/sec    1.07    167.1±3.93µs    17.7 MB/sec
linter/default-rules/pydantic/types.py     1.00      2.8±0.04ms     9.2 MB/sec    1.03      2.9±0.04ms     8.9 MB/sec

Windows

group                                      main                                   pr
-----                                      ----                                   --
formatter/large/dataset.py                 1.00      4.9±0.33ms     8.3 MB/sec    1.01      5.0±0.33ms     8.2 MB/sec
formatter/numpy/ctypeslib.py               1.01   993.7±74.88µs    16.8 MB/sec    1.00   986.1±69.83µs    16.9 MB/sec
formatter/numpy/globals.py                 1.00     98.3±6.13µs    30.0 MB/sec    1.04   102.4±11.65µs    28.8 MB/sec
formatter/pydantic/types.py                1.00      2.0±0.14ms    12.7 MB/sec    1.00      2.0±0.13ms    12.7 MB/sec
linter/all-rules/large/dataset.py          1.00     19.0±0.71ms     2.1 MB/sec    1.00     19.0±0.60ms     2.1 MB/sec
linter/all-rules/numpy/ctypeslib.py        1.01      5.1±0.22ms     3.2 MB/sec    1.00      5.1±0.24ms     3.3 MB/sec
linter/all-rules/numpy/globals.py          1.00   629.3±39.42µs     4.7 MB/sec    1.01   637.8±35.68µs     4.6 MB/sec
linter/all-rules/pydantic/types.py         1.00     10.0±0.54ms     2.6 MB/sec    1.00      9.9±0.50ms     2.6 MB/sec
linter/default-rules/large/dataset.py      1.01     10.6±0.65ms     3.9 MB/sec    1.00     10.5±0.59ms     3.9 MB/sec
linter/default-rules/numpy/ctypeslib.py    1.00      2.2±0.08ms     7.7 MB/sec    1.01      2.2±0.16ms     7.6 MB/sec
linter/default-rules/numpy/globals.py      1.00   266.1±18.18µs    11.1 MB/sec    1.00   266.6±16.41µs    11.1 MB/sec
linter/default-rules/pydantic/types.py     1.01      4.6±0.22ms     5.5 MB/sec    1.00      4.6±0.21ms     5.5 MB/sec