Release v0.15.4

What's Changed

• Update stable release to v0.15.3 by @michi-covalent in #1844
• connectivity: Bump test-conn-disrupt img to v0.0.4 by @brb in #1848
• kind: Configure external targets inside the cluster by @michi-covalent in #1846
• chore(deps): update docker.io/library/busybox:stable-glibc docker digest to 7338d0c by @renovate in #1847
• Extend upgrade test for IPsec key rotation test by @jschwinger233 in #1798
• Prepare for v0.15.4 release by @michi-covalent in #1849

Full Changelog: v0.15.3...v0.15.4