[MLIR] Rename test/python/dialects/math.py -> math_dialect.py

[bondhugula]

Summary

Rename test/python/dialects/math.py -> math_dialect.py to avoid a
collision with a Python standard package of the same name. These test
scripts are run by path and are not part of a package. Python apparently
implicitly adds the containing directory to its PYTHONPATH. As such,
test scripts with common names run the risk of conflicting with global
names and resolution of an import for the latter happens to the former.

mlir/test/python/dialects/math_dialect.py

 # RUN: %PYTHON %s | FileCheck %s
 
+# Naming this file with a `_dialect` suffix to avoid a naming conflict with
+# python package's math module (coming in from random.py).
+
 from mlir.ir import *
 import mlir.dialects.builtin as builtin
 import mlir.dialects.math as mlir_math
 
 def run(f):
   print("\nTEST:", f.__name__)
   f()