Fix pattern_from_macro_note for bit-or expr

[ver-nyan]

This is a continuation of issue #99380 (and pr #124488) but covers bit-or pattern.

Essentially a pat1 | pat2, or any bit-or pattern used in a $e:expr was not firing the .pattern_from_macro_note diagnostic bc ast::Expr::is_approximately_pattern() did not cover bit-or.

The cover for bit-or is only added in lower_expr_within_pat(), otherwise doing it in is_approximately_pattern() would result in the suggestion if (i + 2) = 2 => if let (i + 2) = 2 from suggest_pattern_match_with_let() (which is the only other place ast::Expr::is_approximately_pattern() is used from what i see).

resolves #99380
refs #124488

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[ver-nyan]

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mb, it's been a while since i last contributed. Maybe this check can also be added in the git hook?

[fmease]

I'm curious, is there a specific reason why you didn't move this check into is_approximately_pattern? Did it negatively impact other diagnostics that use this method?

Edit: Moving it into that function would also allow you to recurse into the operands to ensure that they're approximately patterns, too.

[ver-nyan]

I initially had it isolated in lower_expr_within_pat() bc it ended up doing an incorrect suggest_pattern_match_with_let()
e.g.

if (i + 2) = 3 {}

help: you might have meant to use pattern matching
   |
LL |     if let (i | 2) = 3 {}
   |        +++

Recursively lhs.is_approximately_pattern() || rhs.is_approximately_pattern() unfortunately didn't work since it would end up matching ExprKind::Lit(_) down the line.

[ver-nyan]

I just learned that undeclared variables are ExprKind::Path, so both Lit and Path will cause false positive let suggestion :c

A more formal example extending tests/ui/expr/if/bad-if-let-suggestion.rs:

if (i + 2) = 3 {} //~ ERROR cannot find value `i` in this scope


error[E0425]: cannot find value `i` in this scope
  --> $DIR/bad-if-let-suggestion.rs:12:9
   |
LL |     if (i | 2) = 3 {}
   |         ^ not found in this scope
   |
help: you might have meant to use pattern matching
   |
LL |     if let (i | 2) = 3 {}
   |        +++

Edit: also i think a recursive approach would lose it's "first-order'ness"

rust/compiler/rustc_ast/src/ast.rs

Lines 1638 to 1639 in 64d5cb6

	/// To a first-order approximation, is this a pattern?
	pub fn is_approximately_pattern(&self) -> bool {