Ppx_profiler: New fix for OCaml 5 (another Parsetree appeared)

What

Backporting @mattiasdrp fix for the profiler, using ppx_lib instead of the parsetree directly.

Manually testing the MR

As usual, from your switch with ocaml5, checkout on 74b5abdc2d and try to build the profiler: dune build src/lib_ppx_profiler. This should result in an error:

Click to expand

File "src/lib_ppx_profiler/rewriter.ml", line 418, characters 63-69:
418 |         | None, None -> Error.error loc Error.(Improper_record record)
                                                                     ^^^^^^
Error: This expression has type
         "(Ppxlib_ast.Ast.longident_loc * Astlib.Ast_414.Parsetree.expression)
         list"
       but an expression was expected of type
         "(Ppxlib.Ast.longident_loc * Parsetree.expression) list"
       Type "Astlib.Ast_414.Parsetree.expression" is not compatible with type
         "Parsetree.expression"
File "src/lib_ppx_profiler/error.ml", line 1:
Error: The implementation "src/lib_ppx_profiler/error.pp.ml"
       does not match the interface "src/lib_ppx_profiler/error.pp.ml": 
       Type declarations do not match:
         type error =
             Invalid_action of string
           | Invalid_payload
           | Invalid_aggregate of Key.t
           | Invalid_custom of Key.t
           | Invalid_mark of Key.t
           | Invalid_record of Key.t
           | Invalid_span of Key.t
           | Invalid_stop of Key.t
           | Improper_field of
               (Longident.t Location.loc *
                Astlib.Ast_414.Parsetree.expression)
           | Improper_let_binding of Astlib.Ast_414.Parsetree.expression
           | Improper_record of
               (Ppxlib.Ast.longident_loc *
                Astlib.Ast_414.Parsetree.expression)
               list
           | Malformed_attribute of Astlib.Ast_414.Parsetree.expression
       is not included in
         type error =
             Invalid_action of string
           | Invalid_payload
           | Invalid_aggregate of Key.t
           | Invalid_custom of Key.t
           | Invalid_mark of Key.t
           | Invalid_record of Key.t
           | Invalid_span of Key.t
           | Invalid_stop of Key.t
           | Improper_field of
               (Longident.t Location.loc *
                Astlib.Ast_414.Parsetree.expression)
           | Improper_let_binding of Astlib.Ast_414.Parsetree.expression
           | Improper_record of
               (Ppxlib.Ast.longident_loc * Parsetree.expression) list
           | Malformed_attribute of Astlib.Ast_414.Parsetree.expression
       Constructors do not match:
         "Improper_record of
           (Ppxlib.Ast.longident_loc * Ppxlib.expression) list"
       is not the same as:
         "Improper_record of
           (Ppxlib.Ast.longident_loc * Parsetree.expression) list"
       The type
         "(Ppxlib.Ast.longident_loc * Astlib.Ast_414.Parsetree.expression)
         list"
       is not equal to the type
         "(Ppxlib.Ast.longident_loc * Parsetree.expression) list"
       Type "Astlib.Ast_414.Parsetree.expression" is not equal to type
         "Parsetree.expression"
       File "src/lib_ppx_profiler/error.mli", lines 8-20, characters 0-44:
         Expected declaration
       File "src/lib_ppx_profiler/error.ml", lines 8-20, characters 0-44:
         Actual declaration

Cherry-pick the patch and compile again: no more error.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR