Improve error on incorrect function/method calls

[john-h-kastner-aws]

Description of changes

Improve parser error messages to more reliably notice that a function or method does exists when it is called with an incorrect number of arguments or using the wrong call style.

For example [].contains(1, 2) now gives the following error where previously it said not a valid method name: `contains` (this message was already given in the cst->est conversion, but not cst->ast).

Error:   × failed to parse policy set
  ╰─▶ call to `contains` requires exactly 1 argument, but got 2 arguments
   ╭─[<stdin>:2:1]
 2 │ 
 3 │ [].contains(1,2)
   · ───────────────
 4 │ 
   ╰────

This PR includes a similar fix for when an extension function is called as a method or an extension method is called as a function.

Checklist for requesting a review

The change in this PR is (choose one, and delete the other options):

• A bug fix or other functionality change requiring a patch to cedar-policy.

I confirm that this PR (choose one, and delete the other options):

• Updates the "Unreleased" section of the CHANGELOG with a description of my change (required for major/minor version bumps).

I confirm that cedar-spec (choose one, and delete the other options):

• Does not require updates because my change does not impact the Cedar Dafny model or DRT infrastructure.

Disclaimer

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