agent-platform release v4.171.0

Added

• Agent-manager 2.16.0 is the floor, github for agents without defaults in #1220 by @teemow
• (toolchains) Source registries and pull secret reach the platform in #1222 by @teemow

Changed

• (deps) Update gsoci.azurecr.io/giantswarm/agent-manager docker tag to v2.17.0 in #1217 by @renovate[bot]

Full Changelog: https://github.com/giantswarm/agent-platform/compare/v4.170.0...v4.171.0