Restrict what APEXes different installers can update

* Mainline APEXes can only be updated by a modulesInstaller (an entry
in whitelisted-staged-installer.xml with isModulesInstaller="true")

* The whitelisted-staged-installer.xml file can have only one entry with
isModulesInstaller="true"

* Vendor APEXes can only be updated by an installer defined in the
corresponding entry in vendor-apex-allowlist.xml.

BYPASS_INCLUSIVE_LANGUAGE_REASON=existing occurrences

Test: atest StagedInstallInternalTest
Test: atest GtsStagedInstallHostTestCases
Test: atest CtsRollbackManagerHostTestCases
Test: atest CtsStagedInstallHostTestCases
Bug: 190802380
Change-Id: I729abb5153df079fb6885016a4b41d0acc827e3c