Added API to change logging levels for JIT (#58821)

Summary:
Description:
- Before this, logging level could only be changed by changing the env
variable "PYTORCH_JIT_LOG_LEVEL"
    - Can change the level from python now
- Have not added stream configuration for now
- Configuration is stored in a singleton class managing the options

Issue Link: https://github.com/pytorch/pytorch/issues/54188

Gotchas:
- Created separate functions
`::torch::jit::get_jit_logging_levels/set_jit_logging_levels` instead of
using the singleton class's method directly
    - This is because when running test cases, two different instances
    of the singleton are created for the test suite and the actual code
    (`jit_log.cpp`)
    - On using these methods directly, `is_enabled` calls the singleton
    in `jit_log.cpp` while we are setting the config using another
    singleton
    - See: https://stackoverflow.com/questions/55467246/my-singleton-can-be-called-multiple-times

API:
- To set the level: `torch._C._jit_set_logging_option("level")`
- To get the level: `torch._C._jit_get_logging_option()`

Testing:
- UTs were added for C++
- A very simple UT was added for python to just check if the API is
being called correctly
- The API was checked by running trace in a sample python file
    - Set env variable to "" and used `_jit_set_logging_option` in python to set the variable to `>dead_code_elimination`
    - The error output had logs of form [DUMP..] [UPDATE...] etc

Fixes https://github.com/pytorch/pytorch/issues/54188

Pull Request resolved: https://github.com/pytorch/pytorch/pull/58821

Reviewed By: soulitzer

Differential Revision: D29116712

Pulled By: ZolotukhinM

fbshipit-source-id: 8f2861ee2bd567fb63b405953d035ca657a3200f

torch/csrc/jit/python/init.cpp

@@ -9,6 +9,7 @@
 #include <torch/csrc/jit/frontend/ir_emitter.h>
 #include <torch/csrc/jit/frontend/tracer.h>
 #include <torch/csrc/jit/ir/irparser.h>
+#include <torch/csrc/jit/jit_log.h>
 #include <torch/csrc/jit/passes/canonicalize.h>
 #include <torch/csrc/jit/passes/canonicalize_graph_fuser_ops.h>
 #include <torch/csrc/jit/passes/common_subexpression_elimination.h>
@@ -639,6 +640,14 @@ void initJITBindings(PyObject* module) {
       .def(
           "_jit_get_inline_everything_mode",
           []() { return getInlineEverythingMode(); })
+      .def(
+          "_jit_get_logging_option",
+          []() { return ::torch::jit::get_jit_logging_levels(); })
+      .def(
+          "_jit_set_logging_option",
+          [](std::string loggingOption) -> void {
+            ::torch::jit::set_jit_logging_levels(loggingOption);
+          })
       .def(
           "_jit_try_infer_type",
           [](py::object obj) -> InferredType {