parse impl types (abstract types) where the lifetime comes first

[m4rch3n1ng]

fixes: #234. i have two notes for this:

one: i had to use a prec(1, to resolve conflicts with _type. i could have also just used a _type instead of the prec(1, choice(, but that would have allowed syntax like impl *const u8 and impl impl dyn Trait, which i don't think should be possible.

the conflict

Error when generating parser

Caused by:
    Unresolved conflict for symbol sequence:
    
      '<'  'impl'  identifier  •  '+'  …
    
    Possible interpretations:
    
      1:  '<'  'impl'  (_type  identifier)  •  '+'  …
      2:  '<'  (abstract_type  'impl'  identifier)  •  '+'  …
    
    Possible resolutions:
    
      1:  Specify a higher precedence in `_type` than in the other rules.
      2:  Specify a higher precedence in `abstract_type` than in the other rules.
      3:  Add a conflict for these rules: `_type`, `abstract_type`

two: as a drive-by-fix in 36e527b, i simplified the bounded_type rule, and also made it more correct. previously it would not allow impl use<'a> + 'a + Trait, which it should syntactically according to the reference. i fixed this here, because (at least in my testing) it doesn't actually change anything and i thought it would be a little silly as an extra pr, but i can split it out if you want me to.

as usual, the diff for the rustc test suite (#229):

the diff

--- .tmp/list.txt	2025-02-28 16:16:12.002933806 +0100
+++ .tmp/list.txt.impl-lifetime-first	2025-03-01 00:04:53.211638735 +0100
@@ -167,8 +167,6 @@
 tests/ui/hygiene/trait_items-2.rs
 tests/ui/hygiene/traits-in-scope.rs
 tests/ui/impl-trait/equality-rpass.rs
-tests/ui/implied-bounds/dyn-erasure-no-tait.rs
-tests/ui/implied-bounds/dyn-erasure-tait.rs
 tests/ui/imports/extern-crate-used.rs
 tests/ui/imports/import-glob-crate.rs
 tests/ui/imports/local-modularized-tricky-pass-2.rs
@@ -176,7 +174,6 @@
 tests/ui/inline-const/const-match-pat-range.rs
 tests/ui/inline-const/pat-unsafe.rs
 tests/ui/issues/issue-22471.rs
-tests/ui/issues/issue-26186.rs
 tests/ui/issues/issue-36116.rs
 tests/ui/issues/issue-37051.rs
 tests/ui/issues/issue-37733.rs
@@ -315,8 +312,6 @@
 tests/ui/try-trait/yeet-for-result.rs
 tests/ui/type-alias-impl-trait/closure_parent_substs.rs
 tests/ui/type-alias-impl-trait/issue-57611-trait-alias.rs
-tests/ui/type-alias-impl-trait/issue-58662-coroutine-with-lifetime.rs
-tests/ui/type-alias-impl-trait/issue-58662-simplified.rs
 tests/ui/type/type-alias-bounds.rs
 tests/ui/type_length_limit.rs
 tests/ui/typeck/auxiliary/tdticc_coherence_lib.rs