SL-409 - fixed some longstanding errors with viewer asset metrics with wrong values being used for sample counts

SL-409 - debug setting to enable/disable use of ViewerAsset cap by asset type. Temporary construction until UDP path goes away.

MAINT-6994 Viewer still reports remaining capacity incorrectly during the presence of an region object bonus.

MAINT-6551 One of my avatars does not render correctly when ALM is disabled unless basic shaders are also disabled.

MAINT-6910 - [MAINT-RC] Some mesh turns invisible when camera is moved on the Maint-RC viewer only - caused by fix for MAINT-6125.

Commulative fix.
Fixed for booth ticket's in indra/newview/llvovolume.cpp
Remained fixed, it's a small code improvements which is not related to
MAINT-6125, MAINT-6910

MAINT-6551 One of my avatars does not render correctly when ALM is disabled unless basic shaders are also disabled.

MAINT-6979 Scroll bar in Appearance -> Wearing jumps up to the top each time an attachment is detached

This is the function in indra/llmessage/tests/testrunner.py that iterates
through ports in a specified range, looking for an available one. Other
platforms understand a specification of port 0 to mean: "You pick one. I'll
just use whichever one you picked."