SL-13565, remove SL-10625 throttling erroneously applied to all GPUs

Remove the sleep throttle applied in 10625 to work around an Intel GPU driver
bug. It was erroneously being applied to all GPUs, and also as of Intel driver
26.20.100.7755 (1/9/2020) it appears that the driver bug no longer exists.

Merge master 6.4.8 into DRTVWR-497

following promotion of DRTVWR-501

Approved-by: Dave Houlton

Merge master v6.4.7 to LMR#4 DRTVWR-497

to reflect previous commit and use correct pool size

following promotion of DRTVWR-476

This reverts commit bf999f2f due to revert of updater, this will be moved to separate 'epic' instead

This fails at teamcity due to missing LLTrans, but builds locally without issues. Reverting to not hold D501

SL-13521 Add avatar appearance lighting to deferred lighting path

Approved-by: Andrey Kleshchev
Approved-by: Michael Pohoreski

This reverts commit 31d9930a.

SL-13406 fix an end-scope enable error in glow rendering

Nat's suggested improvement to LLThreadSafeQueue that takes account of queue being empty as well as the status flag condition

SL-13406, glow disable no longer breaks rendering

Approved-by: Michael Pohoreski