[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/smartCasts/varnotnull/varNull.fir.kt

@@ -3,4 +3,4 @@ fun foo(): Int {
     var s: String? = "abc"
     s = null
     return s.<!INAPPLICABLE_CANDIDATE!>length<!>
-}
+}