PYTHON-5508 - Add built-in DecimalEncoder and DecimalDecoder #8041

Job	Run time
static	4m 51s
Make an sdist	12s
DocTest	1m 9s
Test using minimum dependencies and supported Python	45s
Docs Checks	30s
Link Check	1m 40s
Typing Tests (3.9)	1m 5s
CPython pypy-3.10-ubuntu-latest	12m 24s
CPython 3.9-ubuntu-latest	11m 9s
CPython 3.13t-ubuntu-latest	11m 30s
Test async's minimum dependencies and Python	46s
Typing Tests (3.11)	1m 10s
Install from SDist and Test	57s
	48m 8s

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