Various fixes to C++ domain and format_signatures #1655

Job	Run time
check_conventions (ruff_format ruff_lint check_yaml check_json check_toml check_eof check_trailin...	42s
check_conventions (mypy, 3.9)	32s
check_conventions (mypy, 3.10)	26s
check_conventions (mypy, 3.11)	27s
check_conventions (mypy, 3.12)	29s
build (ubuntu-latest, 3.x, 16.x)	2m 21s
build (windows-latest, 3.x, 16.x)	6m 47s
build (macos-latest, 3.x, 16.x)	2m 37s
compare-wheels	8s
test (ubuntu-latest, 3.9, 16.x)	3m 53s
test (ubuntu-latest, 3.10, 16.x)	3m 56s
test (ubuntu-latest, 3.11, 16.x)	4m 19s
test (ubuntu-latest, 3.12, 16.x)	5m 23s
test (windows-latest, 3.9, 16.x)	9m 24s
test (windows-latest, 3.10, 16.x)	10m 52s
test (windows-latest, 3.11, 16.x)	10m 30s
test (windows-latest, 3.12, 16.x)	10m 24s
test (macos-latest, 3.9, 16.x)	3m 20s
test (macos-latest, 3.10, 16.x)	3m 40s
test (macos-latest, 3.11, 16.x)	3m 43s
test (macos-latest, 3.12, 16.x)	3m 54s
coverage-report	37s
python-publish-package	0s
	1h 28m 24s

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