docs: add stacked pytest parametrize how-to for inline snapshots #1615

Job	Run time
mypy (3.10)	18s
mypy (3.13)	23s
mypy (3.12)	18s
mypy (3.14)	18s
mypy (3.9)	20s
mypy (3.11)	17s
test (3.12, ubuntu-latest, "--with=pydantic>2", false)	5m 56s
test (3.10, ubuntu-latest, "--with=pydantic>2", false)	1m 57s
test (3.9, windows-2022, "--with=pydantic>2", false)	3m 6s
test (3.10, ubuntu-latest, "--with=pydantic<2", false)	2m 6s
test (pypy3.11, ubuntu-latest, "--with=pydantic>2", false)	1m 4s
test (3.9, windows-2022, "--with=pydantic<2", false)	3m 10s
test (3.14, macos-14, "--with=pydantic>2", false)	1m 51s
test (3.9, ubuntu-latest, "--with=pydantic<2", false)	1m 49s
test (3.13, ubuntu-latest, "--with=pydantic>2", false)	2m 0s
test (3.14, ubuntu-latest, "--with=pydantic>2", false)	2m 17s
test (3.11, ubuntu-latest, "--with=pydantic>2", false)	2m 5s
test (3.13, ubuntu-latest, "--with=pydantic<2", false)	1m 43s
test (3.9, macos-14, "--with=pydantic<2", false)	2m 5s
test (3.9, macos-14, "--with=pydantic>2", false)	1m 32s
test (3.9, ubuntu-latest, "--with=pydantic>2", false)	2m 12s
test (3.11, ubuntu-latest, "--with=pydantic<2", false)	1m 58s
test (pypy3.11, ubuntu-latest, "--with=pydantic<2", false)	1m 10s
test (3.12, ubuntu-latest, "--with=pydantic<2", false)	5m 28s
test (3.14, windows-2022, "--with=pydantic>2", false)	3m 32s
Combine & check coverage	12s
Publish new release	14s
	49m 21s

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