Increase the guardrail limit for memory usage per config

+ Current guardrail for memory usage is too conservative, resulting lots of voluntary data drops
in statsd without trying to send broadcast.

+ Actual data upload size is smaller than the in memory data size. So keep the threshold to send
broadcast but lift the memory usage guardrail to give a chance to send broadcast.

+ Also, make byteSize() estimation less frequent.

Bug: 119773948
Test: statsd_test passes
Change-Id: Ia4c660eb47e6d442c0952628e910b494174279d0