Symbol Canonicalization, Loop-Invariant Code Motion, and AST Factory

See merge request !373

Fix handling of constness in Typifier

See merge request !372

Various fixes to constants

See merge request !371

Fix typing of constants

See merge request !370

 - Set not-yet-migrated stages to manual and allow_failure
 - Fix flake8 errors

Squashed commit of the following:

commit fb5c7f843791730450759775580f290e9b323d3a
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 18:12:03 2024 +0100

    set legacy tests to manual execution

commit 1538a1f31e5eadaeaebd5c2adafee36cb2240817
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 18:09:46 2024 +0100

    rename test stage

commit e55bb72157e2796e80fce0c86a4fe63ecfde2753
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 18:08:36 2024 +0100

    fix flake8

commit 3d365ffa00898a1f2b2f7fcd41c9db0857a7169c
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 18:05:18 2024 +0100

    refactor CI: Only fail on nbackend unit tests

commit d5af84f9ef766625dba3f0f21e16d01cea89538e
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 17:59:22 2024 +0100

    fix iteration space test cases

 - Add `select_function` to `Platform` and implement it for `GenericCpu`
 - Add `SelectFunctions` AST pass

Squashed commit of the following:

commit e6b3aa856d2471b645f39d20673eb5259f7b1e1c
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 17:15:55 2024 +0100

    add select_function stub to GenericGpu

commit 679428f053d6bfd3a5ba4d1d1ff6c903577e9ed3
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 17:14:16 2024 +0100

    Remove IntrinsicsError in favor of MaterializaitonError. Move the latter to `backend.exceptions`.

commit 1a01cfde2f39b3394935c2a313312097d4cf66e0
Merge: d73d24c 0e4677de
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 17:07:31 2024 +0100

    Merge branch 'backend-rework' into b_function_mat

commit d73d24cf038950f2129e717a43dd09df11d725c0
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Tue Mar 26 18:19:08 2024 +0100

    introduce SelectFunctions and select_function protocol

commit 671f0578a39e452504243019dab28d93f0114082
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Tue Mar 26 16:39:43 2024 +0100

    Fix documentation for Typifier and PsExpression

commit 3ec258517ad8a510118265184b5dc7805128dcd3
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Mon Mar 25 17:14:21 2024 +0100

    Typing refactor:

      - Annotate all expressions with types
      - Refactor Typifier for cleaner information flow and better
        readability
      - Have iteration space and transformers typify newly created AST nodes

 - Add a `dtype` member to all expression nodes
 - Make the `Typifier` apply `dtype`s to all expressions
 - Adapt transformations and IterationSpace to set data types on created
   expressions
 - Refactor TypeContext and contextual typing interface to be more
   intuitive
 - Refactor the Typifier to apply more operations through the
   TypeContext

Squashed commit of the following:

commit 3e81188a318aa1dc294cf0cd11bf2ec7f62a9b55
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 17:00:17 2024 +0100

    Improve typification of integer expressions

     - Check integer type constraint in `_apply_target_type` to correctly catch deferred expressions

commit 63d0cfa5ea1b8a41c9a74bbfcf0618fad03ffa48
Merge: 671f057 075ae357
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Wed Mar 27 16:46:28 2024 +0100

    Merge branch 'backend-rework' into b_refactor_typing

commit 671f0578a39e452504243019dab28d93f0114082
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Tue Mar 26 16:39:43 2024 +0100

    Fix documentation for Typifier and PsExpression

commit 3ec258517ad8a510118265184b5dc7805128dcd3
Author: Frederik Hennig <frederik.hennig@fau.de>
Date:   Mon Mar 25 17:14:21 2024 +0100

    Typing refactor:

      - Annotate all expressions with types
      - Refactor Typifier for cleaner information flow and better
        readability
      - Have iteration space and transformers typify newly created AST nodes

Integer functions

See merge request !368

Improve comment support

See merge request !367

  - remove DivFunc
  - Fix various imports
  - Move node_collection, isl, kernel_constraints_check to old