[FIR] Improve diagnostic reporting & don't use error symbol for candidate if possible

Also introduce few new diagnostics:
- NONE_APPLICABLE more many inapplicable candidates
- HIDDEN for visible candidates

compiler/testData/diagnostics/tests/checkArguments/SpreadVarargs.fir.kt

@@ -58,7 +58,7 @@ fun main() {
     val x1 = joinT(1, "2")
     checkSubtype<String?>(x1)
     val x2 = <!INAPPLICABLE_CANDIDATE!>joinT<!>(*1, "2")
-    <!INAPPLICABLE_CANDIDATE!>checkSubtype<!><String?>(x2)
+    checkSubtype<String?>(x2)
     val x6 = joinT(1, *a)
     checkSubtype<String?>(x6)
     val x7 = joinT(1, *a, "3")
@@ -93,4 +93,4 @@ fun <T> joinG(x : Int, vararg a : T) : String {
 
 fun <T: Any> joinT(x : Int, vararg a : T) : T? {
     return null
-}
+}