Added pagination and sorting support for Owners API (#11)

[trivedi089]

This PR introduces pagination and sorting support for the GET /owners endpoint in the Spring Petclinic REST API.

Changes Made:
• Updated OwnerController to accept Pageable as a parameter.
• Modified OwnerRepository and service layer to return Page instead of List.
• Updated JSON response to include standard Spring Data pagination metadata (pageable, totalElements, totalPages, etc.).

Example :
API : GET http://localhost:9966/petclinic/api/owners?page=0&size=5&sort=lastName,asc
Response :
{
"content": [
{ "id": 1, "firstName": "George", "lastName": "Franklin", ... }
],
"pageable": {
"pageNumber": 0,
"pageSize": 5
},
"totalPages": 2,
"totalElements": 10,
"last": false,
"first": true
}