the low latency mode is introduced in the early days of Roslyn to make sure we always hit 50ms typing responsive time in our own perf lab typing test.

basically that mode prevent GC to get into most expensvie blocking gen 2 collection. which is nice most of time, but when we are under low memory sitatuion, not doing blocking gen 2 also means we don't do compact.

and that I believe can cause us to be in a sitatuion such as https://github.com/dotnet/roslyn/issues/6802

this basically let us turn that optimization off sacrifying keystroke responsiveness time to time to have more memory available to us.

this mode is supposed to force blocking gen 2 collection when GC detects its own low memory condition, but that seems not consider when there is some free memory left but all those are fregmented.