Remove Java security context serialization (#2677)

Remove Java security context serialization - it is replaced by JSON security context serialization (optimized as size). Backward incompatible change.
Java security context serialization was not used in default hawkbit runtime out of the box. So, it's assumed none uses it. 
Anyway, if anyone has enabled it, he could, in order to keep backward compatibility, get the java security context serialization from the previous hawkbit releases/commits and register it again as a spring bean in his hawkbit extension.

Signed-off-by: Avgustin Marinov <Avgustin.Marinov@bosch.com>

hawkbit-autoconfigure/src/main/java/org/eclipse/hawkbit/autoconfigure/security/SecurityAutoConfiguration.java

@@ -65,11 +65,12 @@ public class SecurityAutoConfiguration {
     }
 
     /**
-     * Creates a {@link ContextAware} (hence {@link TenantAware}) bean based on the given {@link UserAuthoritiesResolver} and
-     * {@link SecurityContextSerializer}.
+     * Creates a {@link ContextAware} (hence {@link TenantAware}) bean based on the given {@link UserAuthoritiesResolver},
+     * {@link SecurityContextSerializer} and {@link TenantResolver}.
      *
      * @param authoritiesResolver The user authorities/roles resolver
-     * @param securityContextSerializer The security context serializer.
+     * @param securityContextSerializer The security context serializer (optional, if not found the default {@link SecurityContextSerializer#NOP} is used).
+     * @param tenantResolver The tenant resolver (optional, if not found the default {@link DefaultTenantResolver} is used).
      * @return the {@link ContextAware} singleton bean.
      */
     @Bean