Glibc* class now rely on ctypes.Structure

[hugsy]

Description/Motivation/Screenshots

To parse the heap, the old way of either relying on the symbol malloc_state or our own class MallocStateStruct both had issues.
This PR addresses this by simplifying the code and implementing our own ctypes.Structure for both GlibcArena and GlibcHeapInfo. This has the huge advantage taht we can tweak easily the structure themselves as the libc changes them. This is way less error-prone (#854 is one of the latest example of error due to bad offset)

Against which architecture was this tested ?

"Tested" indicates that the PR works and the unit test (i.e. make test) run passes without issue.

• x86-32
• x86-64
• ARM
• AARCH64
• MIPS
• POWERPC
• SPARC
• RISC-V

Checklist

• My PR was done against the dev branch, not main.
• My code follows the code style of this project.
• My change includes a change to the documentation, if required.
• If my change adds new code, adequate tests have been added.
• I have read and agree to the CONTRIBUTING document.