PYTHON-5395 - Add convert_decimal to CodecOptions #8031

Job	Run time
static	3m 5s
DocTest	1m 10s
Test async's minimum dependencies and Python	42s
Typing Tests (3.11)	1m 8s
CPython 3.9-ubuntu-latest	6m 55s
CPython pypy-3.10-ubuntu-latest	6m 54s
Typing Tests (3.9)	1m 12s
CPython 3.13t-ubuntu-latest	6m 53s
Make an sdist	16s
Docs Checks	34s
Test using minimum dependencies and supported Python	41s
Link Check	2m 43s
Install from SDist and Test	51s
	33m 4s

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