Add OnSetWarningAndLimit into TestableNetworkStatsProvider

This change also address left comments at ag/15010113.

Test: m gts && atest \
      GtsNetworkStackHostTestCases:NetworkStatsHostTest#testNetworkStatsProvider
Bug: 191327585
Merged-In: I100668cc6d4cecbaff29d027d37d313dd48854f3
Change-Id: I100668cc6d4cecbaff29d027d37d313dd48854f3
  (cherry-picked from ag/15061296)
1 file changed
tree: b2bc2af7b12a71542f60daa7d76fbf0f03742727
  1. staticlibs/