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
Private-in-file declarations conflict with public overload-equivalent declarations
in other files in the same package.
Move functions for grouping possible redeclarations to OverloadResolver
(since they are used only there).
Refactor redeclarations / conflicting overloads reporting.