ANDROID: cpufreq: track per-task time in state

Add time in state data to task structs, and create
/proc/<pid>/time_in_state files to show how long each individual task
has run at each frequency.
Create a CONFIG_CPU_FREQ_TIMES option to enable/disable this tracking.

Bug: 72339335
Bug: 127641090
Test: Read /proc/<pid>/time_in_state
Change-Id: Ia6456754f4cb1e83b2bc35efa8fbe9f8696febc8
Signed-off-by: Connor O'Brien <connoro@google.com>
[astrachan: Folded the following changes into this patch:
            a6d3de6a7fba ("ANDROID: Reduce use of #ifdef CONFIG_CPU_FREQ_TIMES")
            b89ada5d9c09 ("ANDROID: Fix massive cpufreq_times memory leaks")]
Signed-off-by: Alistair Strachan <astrachan@google.com>