[Polly][Isl] Removing explicit operator bool() from isl C++ bindings. NFC.
This is part of an effort to reduce the differences between the custom C++ bindings used right now by polly in `lib/External/isl/include/isl/isl-noxceptions.h` and the official isl C++ interface.
Changes made:
- Removing explicit operator bool() from all the classes in the isl C++ bindings.
- Replace each call to operator bool() to method `is_null()`.
- isl-noexceptions.h has been generated by this https://github.com/patacca/isl/commit/27396daac5a5ee8228d25511a12f4a814c92ba8f
Reviewed By: Meinersbur
Differential Revision: https://reviews.llvm.org/D103976
GitOrigin-RevId: 7c7978a122fdd6eb1bc6300b3a2582108f13ff89
19 files changed
