Fix span suggestion for unstable name collision lint

[ViewWay]

Change the UNSTABLE_NAME_COLLISIONS lint from using plain text help to span_suggestion for method calls, providing users with a visual code replacement suggestion.

Previously:
= help: call with fully qualified syntax Trait::method(...) to keep using the current method

Now:
help: call with fully qualified syntax to keep using the current method
|
LL - receiver.method(args)
LL + Trait::method(...)

Fixes #1794 in rustc_hir_typeck/src/method/probe.rs

[rustbot]

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[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

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[rustbot]

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[chenyukang]

why there is Fixes #1794 in PR description?