Fix stubtest + bind AbstractStateManager dict-protocol

[bjjwwang]

The previous sync (51543e8) added pysvf.AbstractStateManager, AbstractInterpretation and Options to the binary but left the .pyi stub declaring the methods that the same commit removed from AbstractState. The release.yml stubtest job catches that drift and was failing on the sync-llvm-21 PR. This commit:

pybind/AE.cpp:

• Add setitem (delegates to updateAbstractState) and contains (delegates to hasAbstractState) on AbstractStateManager so Python code can use it as a drop-in replacement for the old post_abs_trace dict (Software-Security-Analysis Assignment-3 relies on this to wire the stateMgr in as the post-trace backing store).

pysvf/pysvf.pyi:

• Drop the seven AbstractState methods that the upstream Semi-Sparse refactor moved off the class: getElementIndex, getByteOffset, getPointeeElement, storeValue, loadValue, getAllocaInstByteSize, getGepObjAddrs.
• Add type stubs for AbstractStateManager (full surface, including the dict-protocol additions), AbstractInterpretation, and Options so they are visible to mypy/pyright users.
• Add GepStmt.getStructFieldOffset matching the new lambda binding.

stubtest_allowlist.txt:

• Whitelist the new pybind classes (AbstractStateManager, AbstractInterpretation, Options) using the same pysvf.<Name> shape that already exempts AbstractState/AbstractValue/etc. The pybind11 metaclass + auto-generated __init__(*args, **kwargs) always trip stubtest unless the class is allow-listed.

Verified locally: stubtest reports Success: no issues found in 4 modules.