consolidate AcceptXXXHeader classes into Accept #81

Job	Run time
Validate coverage	31s
Lint the package	1m 4s
Build the documentation	28s
Python: 3.8-x64 on ubuntu-latest	34s
Python: 3.8-x64 on windows-latest	1m 18s
Python: 3.8-x86 on windows-latest	1m 34s
Python: 3.8-x64 on macos-latest	39s
Python: 3.9-x64 on ubuntu-latest	27s
Python: 3.9-x64 on windows-latest	1m 9s
Python: 3.9-x86 on windows-latest	1m 43s
Python: 3.9-x64 on macos-latest	34s
Python: 3.10-x64 on ubuntu-latest	32s
Python: 3.10-x64 on windows-latest	1m 28s
Python: 3.10-x86 on windows-latest	1m 38s
Python: 3.10-x64 on macos-latest	37s
Python: 3.11-x64 on ubuntu-latest	30s
Python: 3.11-x64 on windows-latest	1m 9s
Python: 3.11-x86 on windows-latest	1m 26s
Python: 3.11-x64 on macos-latest	35s
Python: 3.12-x64 on ubuntu-latest	33s
Python: 3.12-x64 on windows-latest	1m 32s
Python: 3.12-x86 on windows-latest	1m 33s
Python: 3.12-x64 on macos-latest	42s
Python: pypy-3.8-x64 on ubuntu-latest	49s
Python: pypy-3.9-x64 on ubuntu-latest	52s
Python: pypy-3.10-x64 on ubuntu-latest	49s
Python: pypy-3.10-x64 on windows-latest	2m 16s
Python: pypy-3.10-x86 on windows-latest	1m 53s
Python: pypy-3.10-x64 on macos-latest	51s
	29m 46s

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