Add helpful message for arity mismatch on function call

[dann-merlin]

What new feature should Elvish have?

When calling a function with an incorrect number of arguments, it would be nice if alongside the exception a helpful message about the function signature, or maybe even the documentation of the function, is displayed.

Example:

~/Programming/elvish> assoc
Exception: arity mismatch: arguments must be 3 values, but is 0 values
  [tty 7]:1:1-5: assoc

could be something like:

~/Programming/elvish> assoc
Exception: arity mismatch: arguments must be 3 values, but is 0 values
expected usage: assoc <container> <k> <v>
  [tty 7]:1:1-5: assoc

Output of "elvish -version"

0.21.0-dev.0.20240628122205-536f2c18dca2

Code of Conduct

• I agree to follow Elvish's Code of Conduct.