[Polly][Isl] Move to the new-polly-generator branch version of isl-noexceptions.h. NFCI

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.

With this commit we are moving from the `polly-generator` branch to the `new-polly-generator` branch that is more mantainable and is based on the official C++ interface `cpp-checked.h`.

Changes made:
 - There are now many sublcasses for `isl::ast_node` representing different isl types. Use `isl::ast_node_for`, `isl::ast_node_user`, `isl::ast_node_block` and `isl::ast_node_mark` where needed.
 - There are now many sublcasses for `isl::schedule_node` representing different isl types. Use `isl::schedule_node_mark`, `isl::schedule_node_extension`, `isl::schedule_node_band` and `isl::schedule_node_filter` where needed.
 - Replace the `isl::*::dump` with `dumpIslObj` since the isl dump method is not exposed in the C++ interface.
 - `isl::schedule_node::get_child` has been renamed to `isl::schedule_node::child`
 - `isl::pw_multi_aff::get_pw_aff` has been renamed to `isl::pw_multi_aff::at`
 - The constructor `isl::union_map(isl::union_pw_multi_aff)` has been replaced with the static method `isl::union_map::from()`
 - Replace usages of `isl::val::add_ui` with `isl::val::add`
 - `isl::union_set_list::alloc` is now a constructor
 - All the `isl_size` values are now wrapped inside the class `isl::size` use `isl::size::release` to get the internal `isl_size` value where needed.
 - `isl-noexceptions.h` has been generated by https://github.com/patacca/isl/commit/73f5ed1f4d1f72582f731590ef9e43d9ab1956ad

No functional change intended.

Reviewed By: Meinersbur

Differential Revision: https://reviews.llvm.org/D107225