Add an escape to String.format()

[luckyabsoluter]

There is no escape for printing {} in String.format().
You cannot print {hi} is bye.

print("{hi} is {hi}".format({"hi": "bye"})) #bye is bye
print("{{hi}} is {hi}".format({"hi": "bye"})) #{bye} is bye
print("\\{hi\\} is {hi}".format({"hi": "bye"})) #\{bye\} is bye

In Python, {{ and }} are escaped in f"}}format{{".
However, GDScript is being used in a different way because of that.
#5391
But you can use "{{{gender}}}" instead of "{{gender}}".
Also, you can use "{{{{{{{gender}}}}}}}" instead of "{{{gender}}}".

Since String.c_unescape() does not support \u, the following is also not possible.

print("\\u007Bhi\\u007D is {hi}".c_unescape()) #\u007Bhi\u007D is {hi}
print("\\u007Bhi\\u007D is {hi}".format({"hi": "bye"}).c_unescape()) #\u007Bhi\u007D is bye

godotengine/godot#38716

Currently, you can use the following:

print("{leftbrace}hi{rightbrace}".format({"hi": "bye", "leftbrace":"{", "rightbrace": "}"})) #{hi}
print("{{}hi{}}".format({"hi": "bye", "{": "{", "}": "}"})) #{hi}

Since this does not seem like the normal way, a new method should be introduced.