Add a `--dry-run` flag to the `install` command

[Flowrey]

What does this PR try to resolve?

This PR add the --dry-run flag to the cargo install command (see #11123). I've tried to do the bare minimal for this flag to work without changing anything in the output.

In my opinion, the --dry-run flag should mimic as close as possible the behavior of the normal command to avoid missing potential issue in the normal execution. ~~Currently we're missing information about where the binary will be installed.~~

Unlike #13598 this PR:

• Include as much of the compilation process as possible without actually compiling
• use the information provided by BuildContext instead of InstallablePackage::new
• in the same way as unit_graph, it add a dry_run to the CompileOptions and return a Compilation::new from the function compile_ws without actually compiling.
• keeps the output the same rather than adding status messages indicating which very broad actions would be performed
• ~~remove some warning not relevant in the case of a --dry-run~~

Like #13598, the version check and crate downloads still occur.

How should we test and review this PR?

The first commit include a unit tests to ensure that no binary is actually installed after the dry run. There is also a snapshot test that show the diff output of the --help flag.

Additional information

Tests and documentation done in #13598, may be cherry picked into this PR if needed.

[rustbot]

r? @ehuss

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[ehuss]

r? epage If you don't mind, feel free to reassign if you are too busy.

[epage]

Note: I tweaked the commits to make this easier to review.

[Flowrey]

Note: I tweaked the commits to make this easier to review.

Thanks, sorry if i made a mess with the commits :sweat_smile:

[weihanglo]

@bors r+

[bors]

:pushpin: Commit b0e08fcd3278b727a4492832316c39efd5433d77 has been approved by weihanglo

It is now in the queue for this repository.

[bors]

:hourglass: Testing commit b0e08fcd3278b727a4492832316c39efd5433d77 with merge d7bffc302ef83dd8a4bf06bd4fb7579e7988263e...

[bors]

:sunny: Test successful - checks-actions Approved by: weihanglo Pushing d7bffc302ef83dd8a4bf06bd4fb7579e7988263e to master...