Add pattern matching instanceof

[coehlrich]

22w11a diff 1.18.2-rc1 diff

Fixes the compile error where a generic is assigned into a variable with the type StringReader here in 22w11a.

Doesn't currently support the way ecj compiles pattern matching instanceof which does the cast twice and check if the casts are the same as well as registering the generated variable in the local variable table.

[pupnewfster]

Wouldn't a better solution be to rebase against upstream which in theory has had this support since early december? https://github.com/MinecraftForge/FernFlower/commit/91cf425e9b35d7cf4816d15ecc8a4422cba87d86

[zml2008]

Closing in favor of #114, thanks though!

[SizableShrimp]

This appears to be a draft because it supposedly has improvements over upstream which need to be rebased & reevaluated.