[jsligo] function parameter destructuring, and let destructuring improvement

type:added

closes #1405 (closed)

• function parameter destructuring taken from !1575 (closed) (unfortunately wasn't merged before..)
• I did not really understand the code (nested_match_repr, nestrec, fold_nested_z ..) so I cleaned it up a bit (it would be nice to review those deletions)

Changelog details:

• JSLIGO patterns in function parameters are now compiled to pattern matching, which improves the generated code in general
• JSLIGO "let-destructuring" will now work on objects (record type) and arrays (tuple type) as in:

let destruct_tuple = (x : [ int , [int , nat] ]) : nat => {
  let [a,[b,c]] = x ;
  c
};

let destruct_record = (x : { a : int , b : string }) : int => {
  let { a , b } = x ; (* Note: nested pattern in record are not yet available *)
  a
};