cmake: update API for zephyr_code_relocate to support relocating libraries

Update API for zephyr_code_relocate to support cmake generator expressions,
as well as relocating libraries.

zephyr_code_relocate can now accept a target name to the LIBRARY argument,
which will be converted into a set of source files from that
target to relocate.

Alternatively, files can be passed as a space separated list
or CMake generator expression. This allows users more
flexibility when relocating files. Glob matching functionality is still
available, although the preferred method to do this would now be:

file(GLOB relocate_sources "src/*.c")
zephyr_code_relocate(FILES ${relocate_sources} LOCATION <location>)

Note! This commit breaks support for zephyr_code_relocate until in tree
usages of the API are updated to the new format.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>