This module determines the `cp` command to use based on availability of
the `coreutils` formula and optimizes the command invocation to prefer a
lightweight copy-on-write clone, which is significantly faster than a
full file copy and helps to reduce the risk of exhausting the storage
during the operation.

This replaces `FileUtils.cp` and `system_command! "cp"` with the new
`Utils::Cp` utility where it is expected that the performance
improvement outweighs the cost of the system command invocation.

As per review feedback:

Homebrew#17373 (comment)

As per review feedback:

Homebrew#17373 (review)

As per review feedback:

Homebrew#17373 (review)

As per review feedback:

Homebrew#17373 (review)

Co-authored-by: Mike McQuaid <[email protected]>

Homebrew#17373 (review)

Co-authored-by: Mike McQuaid <[email protected]>

`FileUtils.cp` is implemented with the lightweight `copy_file_range(2)`
syscall on Linux, so it's more performant than the plain `cp` command on
that platform.

cf. Homebrew#17373 (review)

This fixes the test for `UnpackStrategy::Directory`, which needs the
`cp` command.

As per review feedback:

Homebrew#17373 (comment)