[DASH] Update DASH eni & port counters (#2251)

This pull request updates DASH (Disaggregated API for SONiC Hosts) counters for ENI (Elastic Network Interface) and port statistics based on requirements from sonic-net/SONiC issue #2139. The PR adds comprehensive telemetry capabilities for tracking session management, TCP state transitions, traffic drops, and High Availability (HA) synchronization.

Changes:

Added FINACK acronym definition to meta/acronyms.txt
Added 5 new port-level drop counters in experimental/saiportextensions.h
Added 65 new ENI statistics covering session tracking, TCP state management, drop reasons, and HA sync metrics in experimental/saiexperimentaldasheni.h

Author: arunp-dev