TX and RX BPS and PPS rates in telemetry gnmi

[aseaudi]

Why I did it
We need in telemetry TX and RX BPS (Bits per second) and PPS (Packets per second)

How I did it
Added in telemetry new options for mapping the RATES table in REDIS COUNTERS_DB

How to verify it
manual test using gnmi client to the new virtual paths

Description for the changelog
Added new virtual paths for TX and RX BPS and PPS in telemetry gnmi
examples:
RATES/Ethernet1/RX_BPS
RATES/Ethernet1/RX_PPS
RATES/Ethernet1/TX_BPS
RATES/Ethernet1/TX_PPS