Implement `CommandSpec` structure #789

Job	Run time
windows (Rust formatting, cargo-fmt-check)	1m 2s
windows (Rust linting, cargo-clippy)	2m 6s
linux (Rust formatting, cargo-fmt-check)	1m 5s
windows (Rust tests, cargo-test)	2m 39s
linux (Rust linting, cargo-clippy)	1m 31s
linux (Rust tests, cargo-test)	2m 36s
linux (Python formatting, black-check-all)	1m 40s
linux (Python import sorting, isort-check-all)	59s
linux (Python type checking, mypy-check-all)	58s
linux (Python linting, pylint-check-all)	1m 0s
linux (Python unit tests, pytest-check-all)	1m 42s
linux (Powershell static analysis, PSScriptAnalyzer-check-all)	56s
check_success	3s
	18m 17s

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