Deprecate self and total time getters and total sample count getter on CpuProfileNode

All of these values are derived from the self samples count and there is no need to evaluate them in v8 when clients can do that when needed on their side.

Also added unsigned GetHitCount() which should be used instead of double GetSelfSamplesCount(). I'm going to deprecate the latter one once Blink has switched to GetHitCount.

BUG=267595
TBR=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/22710006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16119 ce2b1a6d-e550-0410-aec6-3dcde31c8c00