Add gNMI sample app for XR syslog config

[dasomeom]

Includes four boilerplate and seventeen custom apps to configure syslog and debug timestamps for XR data model using gNMI/gNMI: gn-set-xr-infra-syslog-cfg-10-ydk.py - set boilerplate gn-set-xr-infra-syslog-cfg-11-ydk.py - set boilerplate gn-set-xr-infra-syslog-cfg-20-ydk.py - Disable log timestamps gn-set-xr-infra-syslog-cfg-22-ydk.py - Uptime log timestamps gn-set-xr-infra-syslog-cfg-24-ydk.py - Local time log timestamps gn-set-xr-infra-syslog-cfg-26-ydk.py - Local time log/debug timest. gn-set-xr-infra-syslog-cfg-28-ydk.py - Detailed log/debug timestamp gn-set-xr-infra-syslog-cfg-30-ydk.py - Logging console disable gn-set-xr-infra-syslog-cfg-32-ydk.py - Logging buffered gn-set-xr-infra-syslog-cfg-40-ydk.py - Logging archive disk1 gn-set-xr-infra-syslog-cfg-42-ydk.py - Logging archive harddisk gn-set-xr-infra-syslog-cfg-50-ydk.py - ipv4 remote logging server gn-set-xr-infra-syslog-cfg-51-ydk.py - ipv6 remote logging server gn-set-xr-infra-syslog-cfg-52-ydk.py - ipv4 remote logging server w/VRF gn-set-xr-infra-syslog-cfg-53-ydk.py - ipv6 remote logging server w/VRF gn-set-xr-infra-syslog-cfg-60-ydk.py - Logging suppression gn-set-xr-infra-syslog-cfg-62-ydk.py - Logging correlation gn-get-xr-infra-syslog-cfg-10-ydk.py - get boilerplate gn-get-xr-infra-syslog-cfg-11-ydk.py - get boilerplate gn-get-xr-infra-syslog-cfg-20-ydk.py - get syslog service gn-get-xr-infra-syslog-cfg-21-ydk.py - get syslog