PLF-5811: Slowness in suggestion portlet

Fix description: Update PeopleRestServices and SpaceRestServices to use the new methods implemented at SOC-4118:
* Limit the total amount of provided suggestions.
* Get the suggestions only from that sample.

Conflicts:
	component/common/src/main/java/org/exoplatform/platform/common/rest/services/SuggestPeoplePortlet/PeopleRestServices.java
	component/common/src/main/java/org/exoplatform/platform/common/rest/services/SuggestSpacesPortlet/SpaceRestServices.java
	component/common/src/test/java/org/exoplatform/platform/common/rest/services/BaseRestServicesTestCase.java