Minify the sdk targets

Previously, the "sdk" target was a minimal lunch target that only
included enough to build the sdk. But the "sdk_<arch>" targets
redirected to the "sdk_phone_<arch>" targets, which are much bigger
and capable of building a whole emulator.

Building the sdk on products that can build a whole device complicates
the rest of the build system (for example, it starts enforcing dexpropt
works)

Bug: 290798660
Test: m sdk dist sdk_repo device-tests platform_tests on sdk_x86_64-userdebug
Change-Id: I76f38cf19172a5f5fae423175d5e03670137a0df