Fix a crash in the external scanner, convert scanner to use array.h header

[maxbrunsfeld]

This fixes an error where deserialize could accidentally write uninitialized custom_tag_name values into the scanner's state, which caused a crash in the destroy hook.

While we were here, we also got rid of the custom String and Vec types, and switched to using array.h.

[maxbrunsfeld]

Hey @amaanq , sorry I didn't see you had a PR open to use array.h before we went ahead and made the switch. I'd like to proceed with this version, since we made a couple of other improvements, like passing ownership of scanned strings into the Tag, rather than cloning the old string and freeing the old string.

[amaanq]

hey that's totally fine, I think mine was outdated anyways (missing a few minor changes upstream) so this is good

[amaanq]

PS, can I bother you to take a peek at tree-sitter/tree-sitter#3191? It has some really important fixes I'd like you to check out

[maxbrunsfeld]

Yes, I'll take a look at that this week. Thanks!!