[Text Server] Add support for user defined punctuation list, used for word breaking.

[bruvzg]

Adds support for user defined punctuation list, used for word breaking. This PR does not affect spaces and dictionary based breaking, or change any defaults and therefor is not superseding #46691.

Usage example:

var a = TextParagraph.new()
a.custom_punctuation = "R"
a.add_string("test.test_testRtest test", get_theme_font("font"), 16)
print("A: ", TextServerManager.get_primary_interface().shaped_text_get_word_breaks(a.get_rid()))
#A: [(0, 14), (15, 19), (20, 24)]

var b = TextParagraph.new()
b.add_string("test.test_testRtest test", get_theme_font("font"), 16)
print("B: ", TextServerManager.get_primary_interface().shaped_text_get_word_breaks(b.get_rid()))
#B: [(0, 4), (5, 9), (10, 19), (20, 24)]

Bugsquad edit: This closes #29789.

[akien-mga]

Thanks!