refactor: removed old_value and new_value from Change classes #1618

Job	Run time
mypy (3.9)	24s
mypy (3.12)	20s
mypy (3.13)	20s
mypy (3.10)	17s
mypy (3.11)	15s
mypy (3.14)	22s
test (3.9, macos-14, "--with=pydantic>2", false)	2m 20s
test (3.9, ubuntu-latest, "--with=pydantic>2", false)	2m 11s
test (3.9, windows-2022, "--with=pydantic<2", false)	3m 11s
test (3.9, ubuntu-latest, "--with=pydantic<2", false)	2m 25s
test (3.12, ubuntu-latest, "--with=pydantic<2", false)	5m 37s
test (3.11, ubuntu-latest, "--with=pydantic>2", false)	1m 57s
test (3.9, macos-14, "--with=pydantic<2", false)	1m 59s
test (3.12, ubuntu-latest, "--with=pydantic>2", false)	6m 2s
test (3.9, windows-2022, "--with=pydantic>2", false)	3m 13s
test (3.10, ubuntu-latest, "--with=pydantic<2", false)	2m 1s
test (3.14, windows-2022, "--with=pydantic>2", false)	3m 34s
test (3.14, ubuntu-latest, "--with=pydantic>2", false)	2m 5s
test (pypy3.11, ubuntu-latest, "--with=pydantic<2", false)	1m 9s
test (3.13, ubuntu-latest, "--with=pydantic>2", false)	2m 0s
test (3.10, ubuntu-latest, "--with=pydantic>2", false)	1m 57s
test (pypy3.11, ubuntu-latest, "--with=pydantic>2", false)	1m 9s
test (3.14, macos-14, "--with=pydantic>2", false)	2m 28s
test (3.11, ubuntu-latest, "--with=pydantic<2", false)	2m 3s
test (3.13, ubuntu-latest, "--with=pydantic<2", false)	1m 56s
Combine & check coverage	17s
Publish new release	13s
	51m 45s

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