Provide unique name from closures with same name (#488)

In YUL it's possible to declare closure with a same name, but in
different scope, which previously resulted to func name conflict during
LLVM IR construction.
To solve this, track YUL scope when building LLVM IR and a special
counter that increments every time function with the same name exists in
LLVM module.
There's still assert if somehow within the same scope there 2 functions
with the same name, which should be forbidden by Yul

Fixes: #474

---------

Co-authored-by: LJ <81748770+elle-j@users.noreply.github.com>

crates/yul/src/parser/statement/block.rs

@@ -136,6 +136,7 @@ impl Block {
 
 impl PolkaVMWriteLLVM for Block {
     fn into_llvm(self, context: &mut PolkaVMContext) -> anyhow::Result<()> {
+        context.push_function_scope();
         let current_function = context.current_function().borrow().name().to_owned();
         let current_block = context.basic_block();
 
@@ -223,6 +224,7 @@ impl PolkaVMWriteLLVM for Block {
         }
 
         context.pop_debug_scope();
+        context.pop_function_scope();
 
         Ok(())
     }