feat: better repr for WeakCallback objects (#236) #444

Job	Run time
Check Manifest	22s
py3.7 on ubuntu-latest	2m 11s
benchmarks	2m 13s
py3.7 on macos-latest	3m 15s
test magicgui	1m 29s
py3.7 on windows-latest	4m 30s
py3.8 on ubuntu-latest	4m 41s
typing	21s
py3.8 on macos-latest	2m 51s
py3.8 on windows-latest	3m 1s
py3.9 on ubuntu-latest	1m 58s
py3.9 on macos-latest	2m 53s
py3.9 on windows-latest	3m 2s
py3.10 on ubuntu-latest	2m 26s
py3.10 on macos-latest	2m 51s
py3.10 on windows-latest	6m 33s
py3.11 on ubuntu-latest pydantic<2	4m 21s
py3.11 on macos-latest	3m 12s
py3.11 on windows-latest pydantic<2	6m 24s
py3.10 on ubuntu-latest PyQt5	3m 56s
py3.10 on macos-latest PyQt6	3m 19s
py3.10 on ubuntu-latest PySide2	2m 27s
py3.10 on macos-latest PySide6	4m 0s
py3.12-dev on ubuntu-latest	2m 23s
	1h 14m 39s

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