[FIR] Fix the TODO in FirConflictsHelpers

According to
https://github.com/Kotlin/KEEP/blob/master/proposals/enhancing-main-convention.md#rules-and-semantics,
only main function without args may avoid
`CONFLICTING_OVERLOADS`, but since the
jps/jps-plugin/testData/incremental/withJava/other/mainRedeclaration
test dates back to 2015, this is not the
current behavior.

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/impl/FirDeclarationStatusImpl.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.KtSourceElement
 import org.jetbrains.kotlin.descriptors.EffectiveVisibility
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibility
+import org.jetbrains.kotlin.fir.FirImplementationDetail
 import org.jetbrains.kotlin.fir.FirPureAbstractElement
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
 import org.jetbrains.kotlin.fir.declarations.impl.FirDeclarationStatusImpl.Modifier.*
@@ -22,6 +23,9 @@ open class FirDeclarationStatusImpl(
     override val source: KtSourceElement? get() = null
     protected var flags: Int = HAS_STABLE_PARAMETER_NAMES.mask
 
+    @FirImplementationDetail
+    internal val rawFlags get() = flags
+
     operator fun get(modifier: Modifier): Boolean = (flags and modifier.mask) != 0
 
     operator fun set(modifier: Modifier, value: Boolean) {
@@ -182,3 +186,10 @@ open class FirDeclarationStatusImpl(
         return FirResolvedDeclarationStatusImpl(visibility, modality, effectiveVisibility, flags)
     }
 }
+
+@OptIn(FirImplementationDetail::class)
+val FirDeclarationStatus.modifiersRepresentation: Any
+    get() = when (this) {
+        is FirDeclarationStatusImpl -> rawFlags
+        else -> error("Generating modifier representations for ${this::class.simpleName} is not supported")
+    }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/impl/FirResolvedDeclarationStatusImpl.kt

@@ -28,6 +28,11 @@ class FirResolvedDeclarationStatusImpl(
             Modality.FINAL,
             EffectiveVisibility.Public
         ).apply { isSuspend = true }
+        val DEFAULT_STATUS_FOR_SUSPEND_MAIN_FUNCTION = FirResolvedDeclarationStatusImpl(
+            Visibilities.Public,
+            Modality.FINAL,
+            EffectiveVisibility.Public
+        ).apply { isSuspend = true }
     }
 
     internal constructor(