refactor: extract mun_hir_input #1906

Job	Run time
Check	1m 53s
Doctest Rust (ubuntu-latest)	2m 13s
Test C++ Runtime (ubuntu-latest)	4m 7s
Test Rust (ubuntu-latest)	3m 32s
Doctest Rust (windows-latest)	8m 32s
Check Style	1m 57s
Test C++ Runtime (windows-latest)	9m 3s
Doctest Rust (macOS-latest)	1m 40s
Test Rust (windows-latest)	13m 19s
Test C++ Runtime (macOS-latest)	3m 20s
Test Rust (macOS-latest)	2m 33s
Test mdbook	4m 20s
	56m 29s

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