Traefik - v2.7.0

Enhancements:
- [consulcatalog] Watch for Consul events to rebuild the dynamic configuration (#8476 by JasonWangA)
- [healthcheck] Add Failover service (#8825 by tomMoulard)
- [http3] Configure advertised port using h3 server option (#8778 by kevinpollet)
- [http3] Upgrade quic-go to v0.25.0 (#8760 by sylr)
- [hub] Add Traefik Hub Integration (Experimental Feature) (#8837 by jbdoumenjou)
- [k8s/crd,k8s] Allow empty services in Kubernetes CRD (#8802 by tomMoulard)
- [metrics] Support InfluxDB v2 metrics backend (#8250 by sh7dm)
- [plugins] Remove Pilot token setup constraint to use plugins (#8869 by ldez)
- [provider] Refactor configuration reload/throttling (#6633 by rkojedzinszky)
- [rules,tcp] Add HostSNIRegexp rule matcher for TCP (#8849 by rtribotte)
- [tcp] Add muxer for TCP Routers (#8182 by dtomcej)
- [webui,pilot] Add Traefik Hub access and remove Pilot access (#8848 by tomMoulard)
- [webui] Add a link to service on router detail view (#8821 by Tchoupinax)

Bug fixes:
- [hub] Skip Provide when TLS is nil (#9031 by ldez)
- [tcp] Fix TCP-TLS/HTTPS routing precedence (#9024 by rtribotte)
- [webui,hub] Use dedicated entrypoint for the tunnels (#9023 by youkoulayley)

Documentation:
- [hub] Fix Traefik Hub TLS documentation (#8883 by jbdoumenjou)
- Add a Feature Deprecation page (#8868 by ddtmachado)
- Prepare release v2.7.0-rc1 (#8879 by tomMoulard)
- Prepare release v2.7.0-rc2 (#8900 by rtribotte)

Misc:
- Merge current v2.6 into v2.7 (#8984 by kevinpollet)
- Merge current v2.6 into v2.7 (#8958 by tomMoulard)
- Merge current v2.6 into v2.7 (#8899 by rtribotte)
- Merge current v2.6 into master (#8877 by rtribotte)
- Merge current v2.6 into master (#8865 by tomMoulard)
- Merge current v2.6 into master (#8832 by tomMoulard)
- Merge current v2.6 into master (#8793 by tomMoulard)
- Merge current v2.6 into master (#8777 by tomMoulard)
- Merge current v2.6 into master (#8757 by tomMoulard)
- Merge current v2.6 into master (#8754 by tomMoulard)
- Merge current v2.6 into master (#8736 by kevinpollet)
- Merge current v2.6 into master (#8689 by tomMoulard)
- Merge current v2.6 into master (#8666 by tomMoulard)