[ET] Fix serde handling of inf (#6832)

Pull Request resolved: #6799

## Context

I was trying to inspect the ETDump of a Vulkan LLaMa inference run, and experienced an `Exception` stemming from a symbol range containing an infinity.

The full error log is

```
Traceback (most recent call last):
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/sympy/core/expr.py", line 4035, in _mag
    mag_first_dig = int(ceil(log10(xpos)))
OverflowError: cannot convert float infinity to integer

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/__run_lpar_main__.py", line 31, in <module>
    __invoke_main()
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/__run_lpar_main__.py", line 28, in __invoke_main
    run_as_main(module, main_function)
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/__par__/meta_only/bootstrap.py", line 98, in run_as_main
    oss_run_as_main(
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/__par__/bootstrap.py", line 94, in run_as_main
    main()
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/executorch/backends/vulkan/fb/tools/inspector/inspector_cli.py", line 41, in main
    inspector = Inspector(
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/executorch/devtools/inspector/_inspector.py", line 1025, in __init__
    self._etrecord = parse_etrecord(etrecord_path=etrecord)
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/executorch/devtools/etrecord/_etrecord.py", line 318, in parse_etrecord
    edge_dialect_program = deserialize(serialized_artifact)
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/executorch/exir/serde/serialize.py", line 683, in deserialize
    return ExportedProgramDeserializer(expected_opset_version).deserialize(
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/executorch/exir/serde/serialize.py", line 598, in deserialize
    res = GraphModuleDeserializer().deserialize(
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/executorch/exir/serde/export_serialize.py", line 1855, in deserialize
    lower = int(vr.lower)
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/sympy/core/expr.py", line 308, in __int__
    r = self.round(2)
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/sympy/core/expr.py", line 3856, in round
    digits_to_decimal = _mag(x)  # _mag(12) = 2, _mag(.012) = -1
  File "/data/users/ssjia/fbsource/buck-out/v2/gen/fbcode/17b27aeeb079adbf/executorch/backends/vulkan/fb/tools/inspector/__inspector_cli__/inspector_cli#link-tree/sympy/core/expr.py", line 4037, in _mag
    mag_first_dig = int(ceil(Float(mpf_log(xpos._mpf_, 53))/log(10)))
AttributeError: 'Infinity' object has no attribute '_mpf_'
```

This arises because the range of a symbol is `[-inf to inf]`. Since infinity cannot be converted to `int` in Python, an exception is raised.

## Changes

Check if a range bound is negative or positive infinity and set it explicitly instead of converted the symbolic integer to `int`.
ghstack-source-id: 253217725
@exported-using-ghexport

Differential Revision: [D65848116](https://our.internmc.facebook.com/intern/diff/D65848116/)

Co-authored-by: Stephen Jia <[email protected]>

exir/serde/export_serialize.py

@@ -1847,7 +1847,13 @@ def deserialize(
             self.symbol_name_to_range = {}
             if symbol_name_to_range:
                 for k, vr in symbol_name_to_range.items():
-                    lower = int(vr.lower)
+                    if math.isinf(vr.lower) and vr.lower < 0:
+                        lower = -math.inf
+                    elif math.isinf(vr.lower):
+                        lower = math.inf
+                    else:
+                        lower = int(vr.lower)
+
                     if vr.upper >= 2:  # max is >= 2, not sym bool range
                         lower = max(2, lower)
                     self.symbol_name_to_range[k] = symbolic_shapes.ValueRanges(