Auto merge of #10478 - Jarcho:block_eq, r=xFrednet

`SpanlessEq` improvements

fixes #9775

Also includes a simplification to `consts::constant`'s interface since I was already touching the code.

At the start of `eq_expr` the check:
```rust
if !self.inner.allow_side_effects && left.span.ctxt() != right.span.ctxt() {
    return false;
}
```
was removed. This was added in 49e2501 to handle `cfg` macros. This is better handled by the newly added `check_ctxt`.

changelog: [various lints]: Don't consider different `cfg!` expansions to be the same unless they are for the same config.
changelog: [various lints]: Don't consider the expansion of two different macros to be equal, even when they expand to the same token sequence.
changelog: [various lints]: Don't consider two blocks to be equal if they contain disabled code or empty macro expansions, unless those section contain the exact same token sequence.

0 files changed, 0 insertions, 0 deletions