Required at project level because some components use header files in
other components' submodules, and one component with a
submodule (esptool.py) doesn't have or need a component.mk.
New makefile component_wrapper.mk allows some variables to be set
before component.mk is evaluated. This properly fixes problems with
sdkconfig being hard to access in all phases of the build.
Including component_common.mk is no longer necessary and will print a
deprecation warning for components which use it.