FIR checker: rename override checker

We can report more diagnostics than type mismatch, e.g.,
nothing to override, var overridden by val, final override, etc.

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirOverrideChecker.kt

@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.types.AbstractTypeCheckerContext
 import org.jetbrains.kotlin.utils.addToStdlib.min
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
-object FirTypeMismatchOnOverrideChecker : FirRegularClassChecker() {
+object FirOverrideChecker : FirRegularClassChecker() {
     override fun check(declaration: FirRegularClass, context: CheckerContext, reporter: DiagnosticReporter) {
         val typeCheckerContext = context.session.typeContext.newBaseTypeCheckerContext(
             errorTypesEqualToAnything = false,

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/checkers/CommonDeclarationCheckers.kt

@@ -46,11 +46,11 @@ object CommonDeclarationCheckers : DeclarationCheckers() {
         FirLocalEntityNotAllowedChecker,
         FirManyCompanionObjectsChecker,
         FirMethodOfAnyImplementedInInterfaceChecker,
+        FirOverrideChecker,
         FirPrimaryConstructorRequiredForDataClassChecker,
         FirSupertypeInitializedInInterfaceChecker,
         FirSupertypeInitializedWithoutPrimaryConstructor,
         FirTypeParametersInObjectChecker,
-        FirTypeMismatchOnOverrideChecker,
         FirMemberFunctionChecker,
         FirMemberPropertyChecker,
     )