Revised Array Modelling & Memory Model

This MR revises the way C arrays, as well as heap memory and pointers, are modelled and translated by pystencils.

Changes concerning arrays:

• Change PsArrayType to receive a fixed, n-dimensional, nonempty shape, and a non-const, non-array element type
• Change PsSubscript to only work on arrays via an n-dimensional index tuple
• Change PsArrayInitList to an n-dimensional matrix of expressions
• Add contextual and default typing for array declarations and inline array literals

Changes concerning pointers and memory:

• Remove PsDeref
• Introduce PsMemAcc to access memory by pointers
• Assume all non-field raw pointers to be aliases of each other, adapt loop-invariant code motion accordingly
• Introduce mem_acc front-end function for accessing memory by pointer in SymPy

Changes to the typifier:

• Remove constness handling from the type context; only work with non-const data types while processing expressions
• In PsAssignment, use a seperate algorithm to determine the mutated memory object and its constness

changed milestone to %Release 2.0

added feature refactor labels

requested review from @he66coqe

assigned to @da15siwa

added 1 commit

• 95a195ea - Add scalar shapes to array type; generalize to SupportsIndex

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added 1 commit

• fd42decd - fix PsSubscript set_child

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approved this merge request

added 1 commit

• 72531dc1 - fix typifier documentation, rename `items_matrix` to `items_grid`.

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resolved all threads

enabled an automatic merge when the pipeline for 72531dc1 succeeds

mentioned in commit e0945b63

merged

mentioned in task #102 (closed)

mentioned in task #99 (closed)

mentioned in commit lbmpy@7f6f3a57