Fixed CTS EuiccManagerTest on HSUM devices

When EuiccManagerTest runs on HSUM devices, the
EuiccUiDispatcherActivity is running as secondary user and on
a different process than phone process. Fixed by storing the
test component in the phone process. This also fixed a security issue
that any malware can use the shell command to override the Euicc
UI component and mess up the eSIM download procedure.

Fix: 353346528
Test: atest EuiccManagerTest on HSUM device
Flag: EXEMPT bug fix
Change-Id: I3fa872036dc7061e5a38f9d73b9eb57b99e59737