Make preloads_copy.sh a module

Make this new module required by cppreopts.sh. This allows removing
the duplicated PRODUCT_COPY_FILES directive for a bunch of devices
that import both.

Also fix some comments in the script.

Bug: 80508492
Test: lunch aosp_blueline-userdebug; m
Change-Id: I804fc17c43274683716a8c9bb3360ac624a80882
2 files changed