Import g3_shared_lib: boottime_api.

The boottime_api is a shared library separate from boot-time-monitor
which managing api and resource usage for several daemons of Deoxys for
code reusability. Including bmcweb, grpc-blob, boot-time-monitor.

Also removed the test/api_test.cpp since it's already moved to the
g3_shared_lib.

Test result:
 - multi-hosts: https://paste.googleplex.com/5984440182112256
 - multi-hosts with mixed sequence and `TrayPowerCycle`: https://paste.googleplex.com/6198410016980992

Google-Bug-Id: 398991424
Change-Id: I520a4d696cd72f2bcaeb897c00a9f40d50eafa0c
Signed-off-by: Jack Huang <huangweichieh@google.com>