cherry-pick: #14513
depends: https://github.com/sonic-net/sonic-utilities/pull/2939
* Add an ability to configure remote syslog servers
* Add an initial configuration for remote syslog
* Extend YANG module and add unit tests
#### Why I did it
Adding the following functionality to rsyslog feature:
* Configure remote syslog servers: protocol, filter, severity level
* Update global syslog configuration: severity level, message format
#### How I did it
added parameters to syslog server and global configuration.
#### How to verify it
create syslog server using CLI/adding to Redis-DB
verify server is added to file /etc/rsyslog.conf and server is functional.
#### Description for the changelog
extend rsyslog capabilities, added server and global configuration parameters.
#### Link to config_db schema for YANG module changes
[sonic-syslog.yang](https://github.com/sonic-net/sonic-buildimage/blob/master/src/sonic-yang-models/yang-models/sonic-syslog.yang)
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