refactor: rename IDEE_NIGHTLY_RELEASE_WEBHOOK secret to generic SLACK_WEBHOOK

Per review feedback: this is a generic reusable workflow, so the
declared secret name shouldn't bake in a consumer-specific naming
convention. The actual GitHub secret name a caller stores doesn't need
to match this internal declaration unless using secrets: inherit, in
which case it does need to match -- so the stored secrets in each
consumer repo are being renamed to SLACK_WEBHOOK to match, rather than
switching callers from inherit to explicit secret mapping.

Author: madhur310

.github/workflows/vscode-publish-extensions.yml

@@ -176,7 +176,7 @@ on:
       MARKETPLACE_DEPLOY_TOKEN:
         description: "CBWeb internal marketplace publishing token"
         required: false
-      IDEE_NIGHTLY_RELEASE_WEBHOOK:
+      SLACK_WEBHOOK:
         description: "Slack notification webhook"
         required: false
 
@@ -1239,7 +1239,7 @@ jobs:
       - name: Notify Slack
         if: inputs.dry-run != 'true' && github.event.inputs.dry-run != 'true' && needs.publish.result == 'success'
         env:
-          SLACK_WEBHOOK_URL: ${{ secrets.IDEE_NIGHTLY_RELEASE_WEBHOOK }}
+          SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK }}
           RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
           REGISTRIES: ${{ inputs.registries }}
           EXTENSION_NAMES: ${{ steps.extension-details.outputs.extension_display_names }}
@@ -1342,7 +1342,7 @@ jobs:
       - name: Notify Slack
         if: inputs.dry-run != 'true' && github.event.inputs.dry-run != 'true' && (needs.publish.result == 'failure' || needs.bump-versions.result == 'failure' || needs.package.result == 'failure')
         env:
-          SLACK_WEBHOOK_URL: ${{ secrets.IDEE_NIGHTLY_RELEASE_WEBHOOK }}
+          SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK }}
           RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
           REGISTRIES: ${{ inputs.registries }}
           EXTENSION_NAMES: ${{ steps.extension-details.outputs.extension_display_names }}