Add keyword to allow disabling config forwarding in SSHCluster

[jacobtomlinson]

Closes #8138

#8138 shows that in Windows there is a limit to environment variable size, and SSHCluster serialises your Dask config to forward to the remote processes. If your Dask config is really big then this will fail. There isn't a clear solution here, in #4465 we explored compressing config, but that isn't a perfect solution so hasn't been merged.

A reasonable workaround is to be able to just disable this functionality if you don't need it. Users in #8138 (comment) have reported just modifying distributed to disable this. This PR adds a kwarg to officially support disabling config forwarding.

• Tests added / passed
• Passes pre-commit run --all-files

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

    27 files  ±0      27 suites  ±0   11h 40m 27s ⏱️ + 6m 21s
 4 116 tests ±0   4 002 ✅ +2    111 💤 ±0  3 ❌  - 1 
51 615 runs   - 1  49 315 ✅ +2  2 297 💤 +1  3 ❌  - 3 

For more details on these failures, see this check.

Results for commit 76d63b1. ± Comparison against base commit 49f5e74.