Refactor bitness resolving logic of product-installed-files

* Add get-modules-for-2nd-arch helper function

Add a generic function to retrieve second arch variant module names for
TARGET, HOST and HOST_CROSS modules.
It uses ALL_MODULES.<module>.FOR_2ND_ARCH to make sure that we are
really returning second arch variant module names.
Unlike `get-32-bit-modules` this function doesn't sort its output so it
potentially saves us a tiny bit of makefile parsing time.

* Add resolve-bitness-for-modules

Factor out the common bitness-resolving logic of
`product-installed-files` and `host-installed-files` to a helper
function.
When resolving HOST_CROSS modules, the primary arch is 32-bit and
secondary arch is 64-bit.

Bug: 155869107
Test: TH
Test: check the value of product_target_FILES and product_host_FILES
Change-Id: I0fdea2e8c55e5b8edf960dbf5e17bb789abb0bf8