Fix peer warning message requester

[clemyan]

What's the problem this PR addresses?

When an incompatible peer warning occurs, the warning message shown during install simply uses the first peer requester found but that may not have any relation to the unsatisfied request.

See #6205 (comment) (partial fix)

How did you fix it?

Actually find the first unsatisfied requester, prioritizing root requesters (i.e. direct dependencies).

If an unsatisfied root requester is found, the warning message looks similar to 4.2.2

➤ YN0000: ┌ Post-resolution validation
➤ YN0060: │ react is listed by your project with version 18.3.1 (pfa021), which doesn't satisfy what reflux and other dependencies request (but they have non-overlapping ranges!).
➤ YN0086: │ Some peer dependencies are incorrectly met by your project; run yarn explain peer-requirements <hash> for details, where <hash> is the six-letter p-prefixed code.
➤ YN0000: └ Completed

If all root requesters are satisfied, then an unsatisfied requester is found and reported with one of the corresponding root requesters

➤ YN0000: ┌ Post-resolution validation
➤ YN0060: │ react is listed by your project with version 18.3.1 (pfa021), which doesn't satisfy what reflux (via @local/test-reflux-dependent) and other dependencies request 
(but they have non-overlapping ranges!).
➤ YN0086: │ Some peer dependencies are incorrectly met by your project; run yarn explain peer-requirements <hash> for details, where <hash> is the six-letter p-prefixed code.
➤ YN0000: └ Completed

One concern I had was that it will make the message longer, but we are already way past the common terminal width so I don't think that's a big issue.

Checklist

• I have read the Contributing Guide.

• I have set the packages that need to be released for my changes to be effective.

• I will check that all automated PR checks pass before the PR gets reviewed.