Simplify name uniquification in inliner (microsoft#1953)

The current implementation of using the entire call-stack to produce
unique names produces very long names, which makes debugging harder.
Simplify this for now. (We may need some investigation to produce more
meaningful names, which is future work.)

Author: gramalingam

onnxscript/optimizer/_inliner.py

@@ -25,13 +25,14 @@
 def _make_unique_name(name: str, callstack: CallStack, used_names: set[str]) -> str:
     """Generate a unique name from a name, calling-context, and set of used names.
 
-    When a value X in a function is inlined into a graph, we rename X by adding a prefix
-    representing the call-stack of the function. This should typically avoid name clashes.
-    If there is a name clash, even after this, we add a numeric suffix to the name to make
+    If there is a name clash, we add a numeric suffix to the name to make
     it unique. We use the same strategy to make node names unique.
+
+    TODO: We can use the callstack in generating a name for a value X in a function
+    that is inlined into a graph. This is not yet implemented. Using the full callstack
+    leads to very long and hard to read names. Some investigation is needed to find
+    a good naming strategy that will produce useful names for debugging.
     """
-    prefix = "_".join(callstack)
-    name = prefix + "_" + name
     candidate = name
     i = 1
     while candidate in used_names: