PYTHON-5395 - Add convert_decimal to CodecOptions #7997

Job	Run time
CPython 3.13t-ubuntu-latest	42s
Test async's minimum dependencies and Python	47s
CPython pypy-3.10-ubuntu-latest	53s
Typing Tests (3.11)	1m 9s
Typing Tests (3.9)	1m 16s
Test using minimum dependencies and supported Python	40s
CPython 3.9-ubuntu-latest	47s
Make an sdist	18s
static	3m 18s
DocTest	55s
Docs Checks	30s
Link Check	14m 50s
Install from SDist and Test	1m 1s
	27m 6s

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