Set LimitNOFILE for Patroni systemd service

[vitabaks]

This PR adds LimitNOFILE to the Patroni systemd service file to increase the limits for open file descriptors from 1024 to 65536.

New variable: patroni_systemd_limit_nofile, default: 65536

Fixed:

This change helps improve stability and prevent connection failures due to file descriptor limits.

[vitabaks]

Check

for pid in $(pgrep -x postgres); do
  echo "PID: $pid"
  cat /proc/$pid/limits | grep "open files"
done

PID: 1343668
Max open files            65536                65536                files
PID: 1343670
Max open files            65536                65536                files
PID: 1343673
Max open files            65536                65536                files
PID: 1343674
Max open files            65536                65536                files
PID: 1343675
Max open files            65536                65536                files
PID: 1343684
Max open files            65536                65536                files
PID: 1343690
Max open files            65536                65536                files
PID: 1343765
Max open files            65536                65536                files
PID: 1343795
Max open files            65536                65536                files
PID: 1343796
Max open files            65536                65536                files
PID: 1345121
Max open files            65536                65536                files
PID: 1345130
Max open files            65536                65536                files
PID: 1345133
Max open files            65536                65536                files
PID: 1345134
Max open files            65536                65536                files
PID: 1345135
Max open files            65536                65536                files
PID: 1345137
Max open files            65536                65536                files
PID: 1345138
Max open files            65536                65536                files
PID: 1345139
Max open files            65536                65536                files
PID: 1345482
Max open files            65536                65536                files
PID: 1345483
Max open files            65536                65536                files

passed