[v14] Introduce tbot-distroless image

[strideynet]

Backport #38259 to branch/v14

changelog: tbot-distroless image is now published. This contains just the tbot binary and therefore has a smaller image size.

[fheinecke]

@strideynet When writing changelog entries please consider the change from the customer's perspective. Changelog entries should be a short, concise description of what changed and why/if the customer should care. A more appropriate changelog entry would be:

changelog: Added a tbot-only tbot-distroless container image, bringing an 80% size reduction over the Teleport teleport image.