Refactor class/instance loading and resolving in the SLI module

Refactor class/instance loading and resolving in the SLI module

Code from the static class SvcLogicAdaptorFactory is moved
to the SvcLogicClassResolver class.

Class SvcLogicClassResolver is created as a bean in the blueprint xml
file, not as singleton directly in the code. Then is injected via
blueprint into the SvcLogicServiceImpl.

Methods registerExecutor and unregisterExecutor from
the SvcLogicServiceImpl class are removed - are not used anywhere.

This change causes compilation error in the northbound repository.
Fix for this error is here:
https://gerrit.onap.org/r/#/c/ccsdk/sli/northbound/+/95053/

Issue-ID: CCSDK-1688
Change-Id: I26ce01b761ab5d17f1cc19e39af581b1963658a5
Signed-off-by: Samuel Kontris <samuel.kontris@pantheon.tech>