Changes

ci(tekton): use dynamic registry for hotfix builds (#4459)

This pull request updates how the container registry is selected for
Tekton pipeline triggers, making the selection dynamic based on the
event type. Instead of hardcoding the registry, the configuration now
determines whether to use the hotfix or dev registry by inspecting the
event header. This improves flexibility and ensures that hotfix builds
are pushed to the correct registry.

**Dynamic registry selection based on event type:**

* Added a `registry` parameter to multiple trigger files (PR, branch
push, and tag creation), which uses an expression to select the hotfix
or dev registry depending on whether the event type starts with
`net.pingcap.tibuild.hotfix.`
(`tekton/v1/triggers/triggers/env-prod2/_/fake-github/fake-github-branch-push.yaml`,
`fake-github-branch-push-single-platform.yaml`, `fake-github-pr.yaml`,
`fake-github-pr-single-platform.yaml`, `fake-github-tag-create.yaml`,
`fake-github-tag-create-single-platform.yaml`)
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**Parameterization of build registry:**

* Updated the `ksy-dev-build-params.yaml` binding to use the dynamically
determined `registry` value from the trigger extensions, instead of a
hardcoded dev registry value
(`tekton/v1/triggers/bindings/ksy-dev-build-params.yaml`)
 (commit: aa1dc84)