Convert yang-xpath-impl into a JPMS module

Convert yang-xpath-impl into a JPMS module

This is a bit more involved, as we are using a different
javax.inject and do not use osgi.cmpn but
org.osgi.service.component.annotations directly.

The latter results in a dependency on an automatic module, but
that is not really a problem as we never touch them at runtime.

Since we do not want to export out implementation directly, and
it still needs to be discoverable via reflection, we dedicate
org.opendaylight.yang.xpath.impl.di package for that purpose.
It will come in handy for other injection frameworks as well.

JIRA: YANGTOOLS-1145
Change-Id: Ie80b02eba551fa89c334f20484e386d808316ca3
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>