The problem results in broken import quick fix and import optimizer on
the IDE side [1].
`AssignResolutionAltererExtension` introduced a possibility to override
resolution of assignment statements. The inconsistency though is
that `KtSimpleNameReference.getResolvesByNames` doesn't return a name
for the overridden `=`. Kotlin as a language doesn't support this [2].
This commit eliminates the drawback above:
1. It fixes the name `assign` the `=` can be resolved to [3].
This eliminates the need to search for the name, bypassing the
plugins.
2. `KtSimpleNameReference.getResolvesByNames` returns `assign` among
other names in case it deals with binary `=` and assignment is
resolved.
3. `KtCompilerPluginsProvider` was extended to check plugins' presence.
K1 implementation added.
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[1]: https://youtrack.jetbrains.com/issue/KTIJ-24390
[2]: OperatorConventions.getNameForOperationSymbol
https://kotlinlang.org/docs/operator-overloading.html#augmented-assignments
[3]: OperatorConventions#ASSIGN_METHOD + AssignmentPluginNames
All other compiler plugins accept "pkg1.pkg2.Class1" classes notation
and correctly match against it
But Assignment plugin used `ClassId` on such qualified names and got
`ClassId("/pkg1.pkg2.Class1")` instead of `ClassId("pkg1/pkg2/Class1")`,
and that lead to unexpected problems
This commit fixes that by using `FqName` instead of `ClassId`
^KT-57406 Fixed
`candidateSymbol` has any reasonable meaning only for references with
not completed candidate, so this property is moved from FirNamedReference
to new node FirNamedReferenceWithCandidateSymbol, which has real
implementation only in :resolve module (`FirNamedReferenceWithCandidate`)