Bump to Go 1.27.0 / 1.26.7 #22329

What would you like to be added?

Go 1.27.0 was released last week, which means that 1.25 no longer receives updates. According to our Dependency management documentation, we want our stable branches to stay on the oldest supported minor version, and our main branch to stay on the latest.

Progress track:

• etcd
  • main: go v1.27.0 - [DO NOT MERGE] Bump go toolchain to 1.27rc3 #22302
  • release-3.7: go v1.26.7 (no action needed, already at 1.26.7)
  • release-3.6: go v1.26.7 - [release-3.6] Bump go 1.26.7 #22334
  • release-3.5: go v1.26.7 - [release-3.5] Bump go 1.26.7 #22335
  • CHANGELOG
• bbolt
  • main: go v1.26.7 - bump go 1.26.7 bbolt#1269
  • release-1.5: v1.26.7 - [release-1.5] bump go 1.26.7 bbolt#1270
  • release-1.4: v1.26.7 - [release-1.4] bump go 1.26.7 bbolt#1271
  • release-1.3: v1.26.7 - [release-1.3] bump go 1.26.7 bbolt#1272
• raft
  • main: go v1.26.7 - no action needed
  • release-3.7: go v1.26.7 - no action needed
  • release-3.6: go v1.26.7 - [release-3.6] bump go 1.26.7 raft#508
• etcd-io/gofail master: go v1.26.7 - bump go 1.26.7 gofail#162
• etcd-io/auger main: go v1.27.0 - bump go 1.27.0 auger#519
• etcd-io/etcd-operator: go v1.27.0 - bump go 1.27.0 etcd-operator#486
• etcd-io/protodoc master: go v1.26.7 - bump go 1.26.7 protodoc#37

Please review the previous issues and their corresponding pull requests, such as #22309 and #22057.

Why is this needed?

To keep the project on supported Go versions.