Clarify multiple version requirement behavior

[jdraymon]

Clarify handling of multiple version requirements of disjoint regions

What does this PR try to resolve?

Resolves a gap in the existing documentation around the dependency specification for multiple version requirements.

How to test and review this PR?

As only an update to the cargo book, review should be straightforward

[rustbot]

r? @weihanglo

rustbot has assigned @weihanglo.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[weihanglo]

Thanks!

[weihanglo]

https://github.com/rust-lang/cargo/actions/runs/17843149030/job/50737127259#step:15:4717

---- package::reserved_windows_name stdout ----
running `D:\a\cargo\cargo\target\debug\cargo.exe package`

thread 'package::reserved_windows_name' panicked at tests\testsuite\package.rs:2997:10:

test failed running `D:\a\cargo\cargo\target\debug\cargo.exe package`
error: process exited with code 0 (expected 101)
--- stdout

--- stderr
warning: manifest has no documentation, homepage or repository.
See https://doc.rust-lang.org/cargo/reference/manifest.html#package-metadata for more info.
   Packaging foo v0.0.1 (D:\a\cargo\cargo\target\tmp\cit\t2388\foo)
    Updating `dummy-registry` index
    Packaged 4 files, 1.4KiB (877B compressed)
   Verifying foo v0.0.1 (D:\a\cargo\cargo\target\tmp\cit\t2388\foo)
 Downloading crates ...
  Downloaded bar v1.0.0 (registry `dummy-registry`)
   Compiling bar v1.0.0
   Compiling foo v0.0.1 (D:\a\cargo\cargo\target\tmp\cit\t2388\foo\target\package\foo-0.0.1)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.56s

Requeuing