Rollup merge of rust-lang#103867 - compiler-errors:no-has-errors, r=c…

…jgillot

Remove `has_errors` from `FnCtxt`

It doesn't seem like this `has_errors` flag actually suppresses any errors (at least in the UI test suite) --- except for one test (`E0767.rs`), and I think that error really should be considered legitimate, since it has nothing to do with the error code and continues to exist after you fix the first error...

This flag was added by ```@eddyb``` in 6b3cc0b, and it's likely that it was made redundant due to subsequent restructuring of the compiler.

It only affects block type-checking anyways, so its effect does seem limited these days anyway.