renames 'diffsync' fields and variables to 'adapter' #877

Job	Run time
black	37s
validate_renovate	29s
bandit	23s
pydocstyle	26s
mypy	21s
flake8	20s
yamllint	26s
build	1m 2s
pylint	1m 8s
unittest (3.8, 1.5.1)	38s
unittest (3.9, 1.5.1)	42s
unittest (3.10, 1.5.1)	54s
unittest (3.11, 1.5.1)	35s
Push Package to PyPI	0s
Publish to GitHub	0s
Send notification to the Slack	0s
	8m 1s

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