Rollup merge of #122737 - ytmimi:conditionally_ignore_fatal_diagnostic, r=davidtwco

conditionally ignore fatal diagnostic in the SilentEmitter

This change is primarily meant to allow rustfmt to ignore all diagnostics when using the `SilentEmitter`. Back in #121301 the `SilentEmitter` was shared between rustc and rustfmt. This changed rustfmt's behavior from ignoring all diagnostic to emitting fatal diagnostics, which lead to rust-lang#6109.

These changes allow rustfmt to maintain its previous behaviour when using the `SilentEmitter`, while allowing rustc code to still emit fatal diagnostics.

Author: matthiaskrgr

Diff for: src/parse/session.rs

@@ -121,6 +121,7 @@ fn default_dcx(
             fallback_bundle,
             fatal_dcx: DiagCtxt::new(emitter),
             fatal_note: None,
+            emit_fatal_diagnostic: false,
         })
     } else {
         emitter
@@ -209,7 +210,7 @@ impl ParseSess {
             rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(),
             false,
         );
-        self.raw_psess.dcx.make_silent(fallback_bundle, None);
+        self.raw_psess.dcx.make_silent(fallback_bundle, None, false);
     }
 
     pub(crate) fn span_to_filename(&self, span: Span) -> FileName {