Make it possible to configure multiple RELP target servers

[plkokanov]

How to categorize this issue?

/kind enhancement

What would you like to be added:
Make it possible to configure multiple RELP target servers. Additionally, make it possible to choose separate log inputs and logging rules per target. Potentially there could be multiple log inputs per 1 target.

Why is this needed:
This would allow users to forward logs to multiple servers. For instance, audit logs could be forwarded to two logging servers - one where they are kept for short period of time for quick analysis and one where they are kept for longer (cold storage). In addition, this would allow users to use the shoot-rsyslog-relp extension for other logs as well.

[gardener-ci-robot]

The Gardener project currently lacks enough active contributors to adequately respond to all issues.
This bot triages issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue as fresh with /remove-lifecycle stale
• Mark this issue as rotten with /lifecycle rotten
• Close this issue with /close

/lifecycle stale

[gardener-ci-robot]

The Gardener project currently lacks enough active contributors to adequately respond to all issues.
This bot triages issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue as fresh with /remove-lifecycle rotten
• Close this issue with /close

/lifecycle rotten