Bug: 120794191
Bug: 123524494
Test: set a property and ensure it can be read in AndroidRuntime.cpp

Change-Id: Ib37102f35e9987d3d9baff83c45571a5d632ad50

Whitelist the persistent system properties that will be used as
flags in activity manager experiments.

Bug: 120794810
Test: m, flash, test getting flag value in ActivityManagerService.java
Change-Id: I90a10bc87d6db3a64347b62fd02e6f0b12ac9fa8

For input experiments that are enabled at boot time, allow system_server
to read and write the device config flags.

Bug: 120794829
Test: presubmit
Change-Id: I0f075a7579c593d4e07c3e31be529e34554068a6

Test: m -j & manually on device
Change-Id: I3f5ddeb26ddf1bf280ef5e7b3e62b4b892b83a3c

For experiment flag testing, we add a flag netd and have
SEPolicy updates.

Test:  add sepolicy, m -j, check GetServerConfigurableFlag function in netd
Bug:122050512
Change-Id: I21c844c277afc358085d80447f16e4c0d4eba5b3

grant rw_dir_perms of dir
/data/server_configurable_flags to flags_health_check.te, in order to
enable flags_health_check to record reset flags data as file under this
dir for later use. See function:
server_configurable_flags::ServerConfigurableFlagsReset for how the
permission is used.

Test: manual on device
Change-Id: I1df7b8cadfbe279f26bf828e9e725ce170a376f7

device_config_flags_health_check_prop is used for enabling/disabling
program flags_health_check which is executed during device booting.
"1" means enabling health check actions in flags_health_check, other
values mean flags_health_check will not perform any action.

Test: build succeeded & manual test
Change-Id: I93739dc5d155e057d72d08fd13097eb63c1193b5

Test: m -j succeeded and manual tested on device

Change-Id: I3415c58335361a9da4ef2368e61bc4e0250a91bb

Test: manual on device
Change-Id: Ibafe1b345489c88a49a7ed3e2e61e5cc5e1880a1