Organize product vars for adding properties

Properties for <partition>/build.prop are now added via
PRODUCT_<PARTITION>_PROPERTIES.

PRODUCT_SYSTEM_PROPERTIES is added. PRODUCT_SYSTEM_DEFAULT_PROPERTIES
will be deprecated.

PRODUCT_VENDOR_PROPERTIES is added. PRODUCT_PROPERTY_OVERRIDES and
PRODUCT_DEFAULT_PROPERTY_OVERRIDES will be deprecated in favor of the new
variable.

For other partitions (odm, system_ext, product), there is no change.

Exempt-From-Owner-Approval: cherry-pick from internal master

Bug: 117892318
Test: m
Merged-In: I98f3b5d0da661b3ad75260a23754e655103b7a44
(cherry picked from commit ad810b6d)
Change-Id: I98f3b5d0da661b3ad75260a23754e655103b7a44