GDScript: Allow Strings and StringNames match each other in a match statement

[rune-scape]

Strings and StringNames match each other in a match statement, dynamically and statically, to make StringName easier to use

• (see discussion in GDScript: Make match behavior consistent (String vs StringName) #74872 and GDScript: Stringy StringNames #75170)

var s = "abc"
var sn = &"abc"

match "abc":
   sn:
   	print("String matches StringName")
   _:
   	assert(false)

match &"abc":
   s:
   	print("StringName matches String")
   _:
   	assert(false)

[adamscott]

Approving this PR for the 4.1 release. The GDScript team approved a part of #75170 (comment) (on April 14th), but asked @rune-scape to create a separate PR with the approved part (this PR). This should make it to this version.

@rune-scape added tests too, so I'm not worried.

[akien-mga]

Thanks!