gardener-extension-provider-metal v0.12.0

This release did not create docker images because the release CI was broken. Please use next release.

General Changes

• Run tests in CI and add test-in-docker target. (#90) @Gerrit91
• Refactor Github Actions (introduce release drafter) and golangci-lint. (#89) @Gerrit91
• Allow updating firewall networks in infrastructure. (#88) @Gerrit91
• Healthcheck controller (#84) @Gerrit91
• Latest codegen and Gardener v1.8 and MCM provider metal (#86) @Gerrit91
• fix build for go 1.15 (#85) @mwennrich
• update to gardener 1.6 (#79) @majst01
• Refactor firewall reconcile. (#71) @Gerrit91