hack: glob-remove all validation-gen outputs in update-codegen.sh

The cleanup step removed only zz_generated.validations.go and left the
per-Kind coverage test fixtures (zz_generated.<version>_test.go,
zz_generated.main_test.go) on disk, so renamed or removed Kinds would
leak stale files. Move every validation-gen output under a shared
zz_generated.validations. prefix and remove them via a single glob.

hack/update-codegen.sh

@@ -420,8 +420,11 @@ function codegen::validation() {
         k8s.io/code-generator/cmd/validation-gen
 
     # TODO: Where do we want these output?  It should be somewhere internal..
-    # The result file, in each pkg, of validation generation.
-    local output_file="${GENERATED_FILE_PREFIX}validations.go"
+    # All files emitted by validation-gen (the per-pkg validations file and the
+    # per-Kind coverage test fixtures under test/declarative_validation/) share
+    # this prefix so the cleanup below can glob-remove them in one pass.
+    local output_file_prefix="${GENERATED_FILE_PREFIX}validations."
+    local output_file="${output_file_prefix}go"
 
     # All directories that request any form of validation generation.
     if [[ "${DBG_CODEGEN}" == 1 ]]; then
@@ -462,14 +465,14 @@ function codegen::validation() {
         done
     fi
 
-    git_find -z ':(glob)**'/"${output_file}" | xargs -0 rm -f
+    git_find -z ':(glob)**'/"${output_file_prefix}"'*' | xargs -0 rm -f
 
     validation-gen \
         -v "${KUBE_VERBOSE}" \
         --go-header-file "${BOILERPLATE_FILENAME}" \
         --output-file "${output_file}" \
         --test-output-root "test/declarative_validation" \
-        --test-output-file-prefix "${GENERATED_FILE_PREFIX}" \
+        --test-output-file-prefix "${output_file_prefix}" \
         --test-allowlist "test/declarative_validation/coverage-allowlist.yaml" \
         --lint-rules=known-tags-only,require-explicit-disablement \
         $(printf -- " --readonly-pkg %s" "${readonly_pkgs[@]}") \