Rollup merge of #127279 - bvanjoi:fix-112680, r=petrochenkov

use old ctx if has same expand environment during decode span

Fixes #112680

The root reason why #112680 failed with incremental compilation on the second attempt is the difference in `opaque` between the span of the field [`ident`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_hir_typeck/src/expr.rs#L2348) and the span in the incremental cache at `tcx.def_ident_span(field.did)`.

-  Let's call the span of `ident` as `span_a`, which is generated by [`apply_mark_internal`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_span/src/hygiene.rs#L553-L554). Its content is similar to:

```rs
span_a_ctx -> SyntaxContextData {
      opaque: span_a_ctx,
      opaque_and_semitransparent: span_a_ctx,
      // ....
}
```

- And call the span of `tcx.def_ident_span` as `span_b`, which is generated by [`decode_syntax_context`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_span/src/hygiene.rs#L1390). Its content is:

```rs
span_b_ctx -> SyntaxContextData {
      opaque: span_b_ctx,
      // note `span_b_ctx` is not same as `span_a_ctx`
      opaque_and_semitransparent: span_b_ctx,
      // ....
}
```

Although they have the same `parent` (both refer to the root) and `outer_expn`, I cannot find the specific connection between them. Therefore, I chose a solution that may not be the best: give up the incremental compile cache to ensure we can use `span_a` in this case.

r?  `@petrochenkov` Do you have any advice on this? Or perhaps this solution is acceptable?

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