Revert "bootstat: Remove custom uptime parser in favor of elapsedRealtime."

This reverts commit 26f40c04c3ad80e2bc449990010d39d1c1b9a5f0.

This change broke the Darwin SDK target.

Test: none
Change-Id: Ia54fe2c31da8d8fa2825e023b035fb8321dcd457
16 files changed