fix: fixed 1st and 3rd point of the to-do list; issue #1162

[andreaVMC]

fixed 1st and 3rd point of the to-do list
This pull request includes significant changes to the heir_py/mlir_emitter.py file to enhance type inference for assignments and return statements. The most important changes include replacing hardcoded types with inferred types and adding a new method to handle type inference.

Enhancements to type inference:

• heir_py/mlir_emitter.py: Modified the emit_assign method to replace the hardcoded type i64 with a call to self.infer_type(assign.value).
• heir_py/mlir_emitter.py: Modified the emit_return method to replace the hardcoded type i64 with a call to self.infer_type(ret.value).

Addition of type inference method:

• heir_py/mlir_emitter.py: Added a new method infer_type to infer types of various expressions, including binary operations, simple data types, lists, tuples, and dictionaries. This method is used in both emit_assign and emit_return to dynamically determine the appropriate type.
  ( issue Resolve experimental python frontend FIXMEs #1162 )

[j2kun]

So I hate to be a naysayer, but this type inference task is a lot more complicated than what is attempted in this PR, and we already have an in-progress PR to implement this feature: #1253.

In the future if you're interested in contributing it would be worthwhile to start a conversation on the GitHub issue or in our discord to discuss the approach before getting into coding.