Generalize everest support to generic 3rdparty support
Generalize everest support to generic 3rdparty support

Other third-party components can now be added by just adding lines to
the definitions of @thirdparty_header_dirs and
@thirdparty_source_dirs.

No semantic change. The output does not change at all.

NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls