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: Presubmits
Change-Id: I0ec5110318c43a7feee0b88edbed1cab0b590a47