[FIX] Fix false-positive constant buffer unregister errors and noisy log.

[Neloreck]

Notes

• Since the parallel render contexts refactor, dx11ConstantBuffer is registered in exactly one per-context registry, but its destructor attempted to unregister from all R__NUM_CONTEXTS registries. Every destroyed buffer produced guaranteed misses in the remaining registries, flooding the log with thousands of ! ERROR: Failed to find compiled constant buffer lines on level unload and renderer teardown — all false positives. With the owning context tracked, the error can only fire on genuine registry corruption.
• Removes 6,680 false positive logs from log file that are appended on game shutdown.

Changes

• Adds m_context_id to dx11ConstantBuffer, stamped by CResourceManager::_CreateConstantBuffer at registration time.
• Replaces the destructor's all-contexts unregister loop with a single targeted _DeleteConstantBuffer(m_context_id, this) call, guarded by RF_REGISTERED and a VERIFY on the context id.
• Extends the failed-unregister error message with the buffer name and context id; adds a GetBufferName() accessor.

Links

Introduced as side effect with #1331