stem property of java modules are propagated to Make

62c7829595c0df53e96addcd347c11ac01012eee introduced the new stem
property to java modules, but it wasn't propagated to Make. Fixing the
problem.

This change also fixes a problem that (module name) == (file name) is
assumed in dexpreopt_config.go, which no longer is the case. A mutator
runs to build a map from module name to its stem. The map is then used
when filling up the file paths in the bootImageConfig struct.

Bug: 139391334
Bug: 143494499
Test: m
Test: BootImageProfileTest
Change-Id: Idbc894f877692401471130de6cbfe5e0dd129da9