[DRA] Remove wait step in buildkite (#15366) (#15391)

DRA artifact builds support two optional parameters
`VERSION_QUALIFIER_OPT` and `DRA_DRY_RUN`.  The most important is
`VERSION_QUALIFIER_OPT` which should be provided when `alpha1` or
similar versions need to be built.

Currently, after clicking new build, the pipeline takes ~20s to
assemble the steps and then pauses the job waiting for these options to be
filled (or just accept the empty defaults) and press continue.

I feel that this could be trappy behavior because the majority of the
use cases don't need it, and it's likely that a user manually clicks
build and forgets that they'd need to confirm these parameters later
on, left with a hanging build.

This commit makes the parameters optional. If needed, they should be
defined explicitly as Environment Variables in the New Build prompt,
after expanding the Options section.

The downside of this approach is that when needed, users need to
consult the documentation about the environment variable names.

(cherry picked from commit 94dfd4773b)

Co-authored-by: Dimitrios Liappis <dimitrios.liappis@gmail.com>

.buildkite/dra_pipeline.yml

@@ -1,28 +1,6 @@
 # yaml-language-server: $schema=https://raw.githubusercontent.com/buildkite/pipeline-schema/main/schema.json
 
 steps:
-  - input: "Build parameters"
-    if: build.source != "schedule"
-    fields:
-      - text: "VERSION_QUALIFIER_OPT"
-        key: "VERSION_QUALIFIER_OPT"
-        default: ""
-        required: false
-        hint: "Optional version qualifier for built artifacts e.g.: alpha1,beta1"
-      - select: "DRA DRY-RUN"
-        key: "DRA_DRY_RUN"
-        required: false
-        default: ""
-        options:
-          - label: "True"
-            value: "--dry-run"
-          - label: "False"
-            value: ""
-        hint: "Whether the DRA release manager will actually publish artifacts, or run in dry-run mode."
-
-  - wait: ~
-    if: build.source != "schedule"
-
   - label: ":pipeline: Generate steps"
     command: |
       set -euo pipefail

.buildkite/scripts/dra/common.sh

@@ -38,10 +38,9 @@ STACK_VERSION=`cat versions.yml | sed -n 's/^logstash\:[[:space:]]\([[:digit:]]*
 
 info "Agent is running on architecture [$(uname -i)]"
 
-export VERSION_QUALIFIER_OPT=$(buildkite-agent meta-data get VERSION_QUALIFIER_OPT --default "")
+export VERSION_QUALIFIER_OPT=${VERSION_QUALIFIER_OPT:-""}
-export DRA_DRY_RUN=$(buildkite-agent meta-data get DRA_DRY_RUN --default "")
+export DRA_DRY_RUN=${DRA_DRY_RUN:-""}
 
 if [[ ! -z $DRA_DRY_RUN && $BUILDKITE_STEP_KEY == "logstash_publish_dra" ]]; then
     info "Release manager will run in dry-run mode [$DRA_DRY_RUN]"
 fi
-