[FIR] Fix resolving of single underscore _

Now compiler throws `UNRESOLVED_REFERENCE` here:

```
val boo = { _: Exception -> `_`.stackTrace }
```

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirLanguageSettingsComponent.kt

@@ -1,16 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.fir
-
-import org.jetbrains.kotlin.config.LanguageVersionSettings
-
-@NoMutableState
-class FirLanguageSettingsComponent(val languageVersionSettings: LanguageVersionSettings) : FirSessionComponent
-
-private val FirSession.languageSettingsComponent: FirLanguageSettingsComponent by FirSession.sessionComponentAccessor()
-
-val FirSession.languageVersionSettings: LanguageVersionSettings
-    get() = languageSettingsComponent.languageVersionSettings

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/BodyResolveContext.kt

@@ -39,6 +39,7 @@ import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.FirImplicitTypeRef
 import org.jetbrains.kotlin.fir.types.coneType
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.name.SpecialNames.UNDERSCORE_FOR_UNUSED_VAR
 
 class BodyResolveContext(
     val returnTypeCalculator: ReturnTypeCalculator,
@@ -612,7 +613,9 @@ class BodyResolveContext(
         valueParameter: FirValueParameter,
         f: () -> T
     ): T {
-        storeVariable(valueParameter)
+        if (!valueParameter.name.isSpecial || valueParameter.name != UNDERSCORE_FOR_UNUSED_VAR) {
+            storeVariable(valueParameter)
+        }
         return withContainer(valueParameter, f)
     }