Added `CallsiteNamespaceAdder` processor #608

Job	Run time
Build & verify package	30s
Verify dev env (ubuntu-latest)	18s
Verify dev env (windows-latest)	52s
Tests & API Mypy on 3.8	47s
Build docs & run doctests	30s
Visual check for color settings using env variables	14s
Type-check package	21s
Tests & API Mypy on 3.9	36s
Tests & API Mypy on 3.10	25s
Pyright	22s
Tests & API Mypy on 3.11	59s
Tests & API Mypy on 3.12	34s
Combine & check coverage.	20s
required-checks-pass	2s
	6m 50s

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