aconfig: update flag info storage file

previously we store three bits per flag: is sticky, is read write, has
override. so when a local override arrives, is sticky bit as well has
override bit are set to true. this becomes problematic when the local
override is removed. we are not sure if we should remove has override
bit as well (server override could still be in place).

therefore restructuring the flag info for each flag into new three bits:
is read write, has server override and has local override. so now server
override and local override bits are independent from each other.

Bug: b/312444587
Test: atest -c
Change-Id: I03b2bb7312480773236c95f2b39f2589fee41924