docs(changelog): update changelog for v1.9.0

[worker-controller-auto-changelog]

Features

• add payload encoding to gate workflow (#528) (ad2dbaa)
• helm: configure kube-rbac-proxy sidecar (#468) (f3bc2ad)

Bug Fixes

• controller: prune Temporal server-side version record on normal drain (#498) (4227ae4)
• controller: delete k8s worker Deployments during WD cleanup (#508) (33585e8)
• pin connection on deprecated versions (#525) (e029d36)
• make 'make test-unit' work out of the box (#499) (9cd89c0)
• clientpool: attach namespace header to every request (#467) (921e5b4)

Documentation

• concepts: warn that changing connectionRef mutates all managed (#512) (16a1fdf)
• changelog: backfill CHANGELOG.md (#524) (bed0114)
• align Worker Options with the API (#500) (dd5978d)

Chores

• added workflow for changelog file (#495) (35fd07e)

Other Changes

• Bump github.com/prometheus/client_golang in /internal/demo (#523) (0943dfc)
• BUG[493] sub-task 1 - complete connection env/volume updates (#516) (46f09ed)
• Bump k8s.io/client-go in / (#521) (261a782)
• Bump docker/login-action from 4.5.0 to 4.6.0 (#518) (3c5a04c)
• standardize all temporal Go package deps (#517) (c8dddf3)
• Updated update-changelog.yml to request reviews from the worker-controller team (#514) (2ca9877)
• [FR-126] Rollback (#274) (6e70184)
• Bump go.temporal.io/api in /internal/demo (#501) (f20efb6)
• Bump docker/login-action from 4.4.0 to 4.5.0 (#503) (2c45961)
• Bump actions/checkout from 7.0.0 to 7.0.1 (#504) (dacd0ec)
• Bump k8s.io/api in / (#506) (bf321ad)
• Skip unavailable deprecated CRD watches (#469) (db62cbb)
• uplift temporal core deps (#490) (3e83925)
• Bump chart version to 0.27.1 [skip ci] (4fd32c8)
• Bump google.golang.org/grpc in / (#487) (d503182)
• tell dependabot to ignore cert-manager dep in Helm (#489) (6c5de89)
• Bump actions/setup-go from 6.5.0 to 7.0.0 (#483) (36eb96a)
• Bump k8s.io/api in / (#488) (220117d)
• uplift temporal core dependencies (#480) (01a92a0)
• Bump google.golang.org/grpc in / (#455) (3f32da9)
• Bump docker/login-action from 4.3.0 to 4.4.0 (#454) (c21a844)
• add Eniko Dif to CODEOWNERS (#464) (01f3d9c)