fixup! [FIR] Remove duplicate diagnostics in metadata by making checkers `DSFAPFO`

Make `FirSyntaxChecker` an expect checker.

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/syntax/FirSyntaxChecker.kt

diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/syntax/FirSyntaxChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/syntax/FirSyntaxChecker.kt
index b603264..e379ba5 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/syntax/FirSyntaxChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/syntax/FirSyntaxChecker.kt
@@ -14,6 +14,7 @@
 import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirDeclarationChecker
 import org.jetbrains.kotlin.fir.analysis.checkers.expression.FirExpressionChecker
 import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
+import org.jetbrains.kotlin.fir.analysis.checkers.CheckerSessionKind
 import org.jetbrains.kotlin.fir.declarations.FirDeclaration
 import org.jetbrains.kotlin.fir.expressions.FirStatement
 
@@ -52,7 +53,7 @@
 }
 
 abstract class FirDeclarationSyntaxChecker<in D : FirDeclaration, P : PsiElement> :
-    FirDeclarationChecker<D>(),
+    FirDeclarationChecker<D>(CheckerSessionKind.DeclarationSiteForExpectsPlatformForOthers),
     FirSyntaxChecker<D, P> {
     final override fun check(declaration: D, context: CheckerContext, reporter: DiagnosticReporter) {
         checkSyntax(declaration, context, reporter)
@@ -60,7 +61,7 @@
 }
 
 abstract class FirExpressionSyntaxChecker<in E : FirStatement, P : PsiElement> :
-    FirExpressionChecker<E>(),
+    FirExpressionChecker<E>(CheckerSessionKind.DeclarationSiteForExpectsPlatformForOthers),
     FirSyntaxChecker<E, P> {
     final override fun check(expression: E, context: CheckerContext, reporter: DiagnosticReporter) {
         checkSyntax(expression, context, reporter)

compiler/testData/diagnostics/tests/multiplatform/headerClass/inheritanceByDelegationInExpectClass.fir.kt

diff --git a/compiler/testData/diagnostics/tests/multiplatform/headerClass/inheritanceByDelegationInExpectClass.fir.kt b/compiler/testData/diagnostics/tests/multiplatform/headerClass/inheritanceByDelegationInExpectClass.fir.kt
index d2d1e55..ebf5924 100644
--- a/compiler/testData/diagnostics/tests/multiplatform/headerClass/inheritanceByDelegationInExpectClass.fir.kt
+++ b/compiler/testData/diagnostics/tests/multiplatform/headerClass/inheritanceByDelegationInExpectClass.fir.kt
@@ -4,6 +4,6 @@
 interface A
 
 class B : A
-<!NO_ACTUAL_FOR_EXPECT{JVM}!>expect class Foo(b: B) : <!IMPLEMENTATION_BY_DELEGATION_IN_EXPECT_CLASS, IMPLEMENTATION_BY_DELEGATION_IN_EXPECT_CLASS{METADATA}!>A by b<!><!>
+<!NO_ACTUAL_FOR_EXPECT{JVM}!>expect class Foo(b: B) : <!IMPLEMENTATION_BY_DELEGATION_IN_EXPECT_CLASS!>A by b<!><!>
 
-<!NO_ACTUAL_FOR_EXPECT{JVM}!>expect class Bar : <!IMPLEMENTATION_BY_DELEGATION_IN_EXPECT_CLASS, IMPLEMENTATION_BY_DELEGATION_IN_EXPECT_CLASS{METADATA}!>A by B()<!><!>
+<!NO_ACTUAL_FOR_EXPECT{JVM}!>expect class Bar : <!IMPLEMENTATION_BY_DELEGATION_IN_EXPECT_CLASS!>A by B()<!><!>