init_python_bindings.cpp: Use new macros for throwing exceptions. (#9595)

Follow-up: #9588 and #9580
Target: `init_python_bindings.cpp` file

In summary, this PR:

- Replaces all calls to `OkOrThrow()` and `GetValueOrThrow()` (that
throws an exception without source location information of the
*"throw-site"*) with the macros `XLA_THROW_IF_ERROR()` and
`XLA_ASSIGN_OR_THROW()`.
- Corresponds to the fine-grained set of PRs that came from breaking
down PR #9580
- Focuses on the `init_python_bindings.cpp` file, replacing every use of
those, now deprecated, functions by the newly introduced macros.

Author: ysiraichi