tests: Add test for Namespace constructor with 3 args #26463

Job	Run time
Paths filter	7s
Check dependencies	1m 31s
Lints with Rust stable	4m 31s
Test Rust stable / ubuntu-24.04	4m 58s
Lints with Rust beta	4m 25s
Test Rust ${{ matrix.rust_version }} / ${{ matrix.os }}	0s
Test Rust stable / windows-latest	14m 56s
Lints with Rust nightly	4m 19s
Test Rust stable / macos-14	3m 48s
Test Rust nightly / ubuntu-24.04	4m 23s
Test Rust beta / ubuntu-24.04	4m 39s
	47m 37s

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