Upgrade TiCDC build toolchain from Go 1.25

Is your feature request related to a problem?

Yes. A customer has phased out Go 1.25 internally, and software built or deployed in their environment can no longer use Go 1.25.

Currently, the TiCDC master branch specifies Go 1.25.12 in go.mod, so the current build toolchain does not meet this requirement.

This is primarily a customer-side security/compliance requirement rather than a TiCDC functional issue.

Describe the feature you'd like

Please upgrade the TiCDC build toolchain from Go 1.25 to a newer supported Go version.

Go 1.26 would satisfy the current customer requirement, but a newer version such as Go 1.27 would also be acceptable.

This should include updating go.mod and any related CI, build images, or build configurations as needed, and verifying that TiCDC can be built and tested successfully with the new Go version.

If feasible, we would also like this change to be backported to the relevant release branch.

Describe alternatives you've considered

No response

Teachability, Documentation, Adoption, Migration Strategy

No response

Start with go.mod and search the CI, build images, and build configurations for references to Go 1.25. Update the toolchain to a newer supported Go version, then verify that TiCDC builds and tests successfully; check whether the change should be backported to a release branch.