Auto merge of #10650 - epage:install, r=ehuss

feat(install): Support `foo@version` like cargo-add

### What does this PR try to resolve?

This aims to make `cargo install` consistent with
- `cargo add foo@version` from #10472
- pkgid changes in #10582
- `cargo yank foo@version` from #10597

It also offers a shorthand for people installing a specific version.

### How should we test and review this PR?

#10582 acted as the FCP for this, see #10597

Documentation updates are split into their own commit to not clog up browsing the code.

Examine the tests to see if they make sense

### Additional information

While the `foo@vewrsion` syntax is the same, each's semantics are different.  We had decided it was better to have the same syntax with different semantics than having the user worry about what syntax they use where.  In `cargo install`s case, it has an
implicit-but-required `=` operand while `cargo-add` allows any operand.

This doesn't use the full `pkgid` syntax because that allows syntax that
is unsupported here.

This doesn't use `cargo-add`s parser because that is for version reqs.

I held off on reusing the parser from `cargo-yank` because they had
different type system needs and the level of duplication didn't seem
worth it (see Rule of Three).

diff --cc tests/testsuite/install.rs
Simple merge