[TD] Update diagnostics test data due to new test runners

Update includes:
- Changing syntax of `OI/`NI` tags from `<!NI;TAG!>` to `<!TAG{NI}!>`
- Fix some incorrect directives
- Change order of diagnostics in some places
- Remove ignored diagnostics from FIR test data (previously `DIAGNOSTICS` didn't work)
- Update FIR dumps in some places and add `FIR_IDENTICAL` if needed
- Replace all JAVAC_SKIP with SKIP_JAVAC directive

compiler/testData/diagnostics/tests/when/ExhaustiveWithNullabilityCheckBefore.kt

@@ -20,4 +20,4 @@ fun foo(arg: X?): Int {
         X.B -> 2
         // else or null branch should not be required here!
     }
-}
+}