Testing framework: add support for mutation in Test.originate_from_file functions

type:added

For LIGO developers

Currently, mutation testing works on reflected values (Test.originate style, env. reconstruction and all that).

This MR adds functions to support mutation of contracts loaded with functions in the style of Test.originate_from_file (which read a .ligo file).

Changelog details:

New functions for testing framework

There are new functions for doing mutation testing directly from files, that originate a mutated version of the contract and then gives control to the passed function that can do the test:

• Test.originate_from_file_and_mutate : string -> string -> string list -> michelson_program -> tez -> (address * michelson_contract * int -> b) -> (b * mutation) option
• Test.originate_from_file_and_mutate_all : string -> string -> string list -> michelson_program -> tez -> (address * michelson_contract * int -> b) -> (b * mutation) list