[HostStubGen] Introduce new feature: method redirection

The existing implementation supports "NativeSubstitution" on classes
with native methods, so that all native methods of that class are
redirected to the "native substitution" class.

Instead of restricting method redirection to native methods (which is
commonly abused to support additional Ravenwood specific methods in
classes), let's properly introduce a mechanism to specify a generic
method redirection.

To reduce code debt, we also migrate all usages of native substitution
to the newly introduced mechanism, and completely remove native
substitution related implementation in HostStubGen.

Bug: 292141694
Flag: EXEMPT host test change only
Test: $ANDROID_BUILD_TOP/frameworks/base/ravenwood/scripts/run-ravenwood-tests.sh
Change-Id: Ic8193f97e59d866957e50202dff101e543430f73