Crashes due to wrong hexadecimal format

[SteMak]

The bytes_required function in sfs_generator/asm_bytecode.py may throw error due to wrongly formatted hexadecimal starting with x prefix

ValueError: invalid literal for int() with base 16: 'xfffffffffffffffffffffffffffffffffffffffffffffffffffffffffff27618'

This happens due to int(string, 16) expects hexadecimal to start with 0x or without prefix at all

I'm not sure where the issue is coming from, I've used --asm-json (--singe-json) mod with quite large contract and the thrown hexadecimal literal is not presented in the asmjson

To resolve the issue, it is necessary to catch where wrong formatted hex value is coming from
The following change can be applied as a hotfix

         if is_push0(self.disasm, self.value):
             return 1
         elif self.disasm == "PUSH":
+            if len(self.value) >= 1 and self.value[0] == "x":
+                self.value = self.value[1:]
             decimal_value = int(self.value, 16)
         else:
             decimal_value = None