Send Dataplane host resources in xDS metadata

[jpeach]

Description

We have a few use cases where Kuma ought to be able to automatically tune envoy based on knowledge of the host environment

• concurrency
• connection limits

To enabled these kinds of features, kuma-dp ought to send some information about its available resources in the bootstrap request, which can then be round tripped through the xDS node metadata.

[jpeach]

triage: Re-evaluate when we look at production readiness more.

[github-actions]

This issue was inactive for 30 days it will be reviewed in the next triage meeting and might be closed.
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[github-actions]

This issue was inactive for 30 days it will be reviewed in the next triage meeting and might be closed.
If you think this issue is still relevant please comment on it promptly or attend the next triage meeting.

[github-actions]

This issue was inactive for 30 days it will be reviewed in the next triage meeting and might be closed.
If you think this issue is still relevant please comment on it promptly or attend the next triage meeting.

[github-actions]

This issue was inactive for 30 days it will be reviewed in the next triage meeting and might be closed.
If you think this issue is still relevant please comment on it promptly or attend the next triage meeting.

[michaelbeaumont]

I think this issue is more of a method for implementing other features. We should simply send the resources we need and introduce them when the time comes.