fix: add `set_fast_math` Method

[iihimanshuu]

Description:

Line 687 in llvmliteir.py calls self.set_fast_math(True) and self.set_fast_math(False), but this method is not defined in the LLVMLiteIRVisitor class. This will cause an AttributeError at runtime when vector operations with fast math are attempted.

File affected:

• llvmliteir.py

Impact: This is a critical bug that would cause runtime failures when using vector operations with fast math attributes.