This call was added to `parse_crate_mod` in #121487, to fix a case where
a stashed diagnostic wasn't emitted. But there is another path where a
stashed diagnostic might fail to be emitted if there's a parse error, if
the `build` call in `parse_crate_inner` fails before `parse_crate_mod`
is reached.
So this commit moves the `emit_stashed_diagnostic` call outwards, from
`parse_crate_mod` to `format_project`, just after the
`Parser::parse_crate` call. This should be far out enough to catch any
parsing errors.
Fixes#121517.
Commit 72b172b in #121206 changed things so that
`emit_stashed_diagnostics` is only called from `run_compiler`. But
rustfmt doesn't use `run_compiler`, so it needs to call
`emit_stashed_diagnostics` itself to avoid an abort in
`DiagCtxtInner::drop` when stashed diagnostics occur.
Fixes#121450.
