Move make_recovery_path and sparse_img to modules.

These two tools are only used within build system, so not adding them
to otatools.zip.

Bug: 63866463
Test: TreeHugger
Test: Build a non-A/B target that calls make_recovery_patch.
Change-Id: Iaeddc98a2c4a27c6b49d91047500029e460db9e3