Build backend: Add `--list` option (#9610)
Add the `uv build --list`, a "subcommand" to list the files that would
be included when building a distribution. It does not build the
distribution, except when a source dist is required for source dist ->
wheel. This is an important debugging tool for the include and exclude
options: Did i actually include the files I wanted, or am i shipping a
broken distribution? Are there any temporary files I still need to
exclude?
Cargo offers this as `cargo package --list`.
`--list` is preview-exclusive, since it requires the fast path, which I
also put into preview.
Examples:
I'll fix the error handling in a follow-up.
Tagging as enhancement because it changes the stable output slightly
(two lines instead of one).
CC @charliermarsh for uv-wide consistency in the stdout/stderr handling.
