issue: #28960
master pr: #28961
add new configuration: builtinRoles
user can define roles in config file: milvus.yaml
there is an example:
db_ro, only have read privileges, include load
db_rw, read and write privileges, include create/drop/rename collection
db_admin, not only read and write privileges, but also user
administration
Signed-off-by: PowderLi <min.li@zilliz.com>
