SL-14167 FIXED Viewer substitutes agni start locations when logging in to 'My last location' on non-agni grids

Don't process EventQueueGet responses from server when disconected

# Conflicts:
#	indra/newview/llviewerregion.cpp

following promotion of DRTVWR-482

Convoluted due to multiple workarounds. Might be a good idea to spend some time refactoring this, but for now just trottled checks.

It is possible for agent to pass multiple region borders fast, resulting in environment updates affecting wrong regions

LLHUDObject has a lot of deriveds stored as LLPointer<LLHUDObject>, no-virtual destructor is unlikely to be cause of the crash, but might be related

LLVOVolume::updateTextures() does not check for null drawable prior to updateTextureVirtualSize

Simplify name generation according to slack discussion, also helps bugsplat with matching files

# Conflicts:
#	indra/newview/llgroupmgr.cpp

following promotion of DRTVWR-497