FIR checker: introduce NO_(GET|SET)_METHOD

Besides introducing new diagnostics, this commit unifies source usages
for array accesses in PSI & LT.

compiler/testData/diagnostics/tests/smartCasts/kt2865.fir.kt

@@ -7,6 +7,6 @@ fun foo(a: MutableMap<String, String>, x: String?) {
 }
 
 fun foo1(a: MutableMap<String, String>, x: String?) {
-    <!INAPPLICABLE_CANDIDATE!>a[x] = x!!<!>
+    <!INAPPLICABLE_CANDIDATE!>a[x]<!> = x!!
     a[x!!] = x
 }