lib: remove prefix-list dup api in validation phase

lib: remove prefix-list dup api in validation phase

Following patch
" lib: disallow access list duplicated values"
introduce a libyang dnode iterator for every prefix-list
config which adds an overhead of traversal all prefix dnodes
and degrades the performance in scaled prefix-list config.

This check is not necessary in prefix-list northbound callbacks
as there won't be a case where prefix-list config comes to nb
callback without sequence number.

The dup check is only necessary for the vtysh case for backward
compatiblity reason where cli can be accepted without sequence number.

Ticket: CM-32035
Reviewed By: CCR-11096
Testing Done:

Signed-off-by: Chirag Shah <chirag@nvidia.com>