FIR checker/IDE: Add checker and quickfix for WRONG_MODIFIER_TARGET.

There are only simple checks for `external` and `const` for now. The
rest of the checks (see ModifiersChecker in FE1.0) will be added later.

compiler/testData/diagnostics/tests/modifiers/const/applicability.fir.kt

@@ -4,7 +4,7 @@ import kotlin.reflect.KProperty
 
 const val topLevel: Int = 0
 const val topLevelInferred = 1
-const var topLeveLVar: Int = 2
+<!WRONG_MODIFIER_TARGET!>const<!> var topLeveLVar: Int = 2
 
 private val privateTopLevel = 3
 

compiler/testData/diagnostics/tests/modifiers/const/types.fir.kt

@@ -12,6 +12,6 @@ const val arrayConst: Array<String> = arrayOf("1")
 const val intArrayConst: IntArray = intArrayOf()
 
 const val unresolvedConst1 = <!UNRESOLVED_REFERENCE!>Unresolved<!>
-const var unresolvedConst2 = <!UNRESOLVED_REFERENCE!>Unresolved<!>
+<!WRONG_MODIFIER_TARGET!>const<!> var unresolvedConst2 = <!UNRESOLVED_REFERENCE!>Unresolved<!>
 const val unresolvedConst3 = <!PROPERTY_INITIALIZER_NO_BACKING_FIELD, UNRESOLVED_REFERENCE!>Unresolved<!>
 get() = 10

compiler/testData/diagnostics/tests/modifiers/modifierOnParameterInFunctionType.fir.kt

@@ -26,7 +26,7 @@ val allProhibited: (<!INCOMPATIBLE_MODIFIERS, REDUNDANT_MODIFIER!>abstract<!>
                     <!INCOMPATIBLE_MODIFIERS!>crossinline<!>
                     <!INCOMPATIBLE_MODIFIERS!>data<!>
                     enum
-                    external
+                    <!WRONG_MODIFIER_TARGET!>external<!>
                     <!INCOMPATIBLE_MODIFIERS!>final<!>
                     <!INCOMPATIBLE_MODIFIERS!>in<!>
                     <!INCOMPATIBLE_MODIFIERS!>inline<!>

compiler/testData/diagnostics/tests/modifiers/repeatedModifiers.fir.kt

@@ -39,3 +39,5 @@ fun test() {
     }
 }
 
+<!WRONG_MODIFIER_TARGET!>external<!> <!REPEATED_MODIFIER!>external<!> val i = 0
+<!WRONG_MODIFIER_TARGET!>const<!> <!REPEATED_MODIFIER!>const<!> var x = 0

compiler/testData/diagnostics/tests/modifiers/repeatedModifiers.kt

@@ -39,3 +39,5 @@ fun test() {
     }
 }
 
+<!WRONG_MODIFIER_TARGET!>external <!REPEATED_MODIFIER!>external<!> val i = 0<!>
+<!WRONG_MODIFIER_TARGET!>const<!> <!REPEATED_MODIFIER!>const<!> var x = 0

compiler/testData/diagnostics/tests/modifiers/repeatedModifiers.txt

@@ -1,6 +1,8 @@
 package
 
 public val bar: kotlin.Int = 1
+public external val i: kotlin.Int = 0
+public const var x: kotlin.Int
 public fun foo(): kotlin.Int
 public fun test(): kotlin.Unit