Clean up some global variables in common.h

Some global variables are only used for recovery.cpp and
recovery_main.cpp, remove them from common.h and handle their usage
accordingly. Variables include:
static constexpr int kRecoveryApiVersion;
extern struct selabel_handle* sehandle;
extern RecoveryUI* ui;
extern bool has_cache;
bool is_ro_debuggable();

Test: unit tests pass, boot into recovery mode and run graphic tests
Change-Id: If83a005786c9b38412731da97aaf85af69a3b917