fix: only evaluate modification time on matched local files

[otosky]

contributes to astronomer/astronomer-cosmos#1075

Description

There is a very hard to reproduce race-condition that occurs in some environments where dbt is used on a concurrently accessed filesystem, like Airflow with Celery workers. The symptom is one process walking the dbt project tree and hitting an error similar to:

  File "/usr/local/airflow/dbt_venv/lib/python3.11/site-packages/dbt/parser/search.py", line 74, in filesystem_search
    for result in find_matching(root, relative_dirs, ext, ignore_spec):
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/airflow/dbt_venv/lib/python3.11/site-packages/dbt/clients/system.py", line 79, in find_matching
    modification_time = os.path.getmtime(absolute_path)
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen genericpath>", line 55, in getmtime
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/tmpf6h80niz/models/intermediate/shipment/.int_easy_post_tracking.sql.GgjJgL'

It's unclear what actually creates those temp files (I would love to know!), but that error should not even occur, since the filename doesn't match any extension spec that dbt should be searching for. Note, I've seen these files created for all extensions that dbt would be concerned with (.md, .yml, .sql); it's not a problem localized to just model files or macros.

This PR reorders the operations in find_matching such that any file names that don't match the regex pattern are skipped before getmtime is even called.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

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