Remove native WebDAV blobstore provider

[WeiQuan0605]

• An explanation of the use cases your change solves:
  • Operators running DAV-backed blobstores can continue using DAV through the storage-cli path (blobstore_type: storage-cli, provider: dav), which is already the path used in cf-deployment. No behaviour change for them.
  • Dependency reduction: removes packages/blobstore_url_signer and the Go binary vendored under src/github.com/cloudfoundry/blobstore_url_signer. (packages/nginx_webdav is retained — the blobstore job's nginx DAV server still depends on it.)
  • CI simplification: removes the blobstore_url_signer git resource from the bump-capi-release pipeline job, which was an extra trigger and submodule bump that no longer has anything to track.
  • Links to any other associated PRs:
    • cloud_controller_ng: Remove native WebDAV blobstore provider cloud_controller_ng#5480
    • cf-deployment: Use storage-cli for WebDAV blobstore cf-deployment#1356 (already migrated to storage-cli)
    • capi-ci: remove blobstore_url_signer pipeline resource Remove blobstore_url_signer from pipeline and bump scripts capi-ci#213
    • community: archive blobstore_url_signer repo Archive blobstore_url_signer repository community#1643

Migration note

Operators with an explicit blobstore_type: webdav in their CC config must migrate before upgrading:

1. Change blobstore_type: webdav to blobstore_type: storage-cli with provider: dav
2. Remove the blobstore job from their deployment

After this change, any deployment still using blobstore_type: webdav will fail at CC boot with:
blobstore_type 'webdav' is no longer supported; use 'storage-cli' with provider 'dav' (see cloud_controller_ng#5480).

Operators using cf-deployment are unaffected — cf-deployment already uses the storage-cli path.

• I have viewed signed and have submitted the Contributor License Agreement

• I have made this pull request to the develop branch

• I have run CF Acceptance Tests on bosh lite

[kathap]

Maybe we need a spec verifying that webdav_config no longer renders in the CC templates?

[kathap]

In config/blobs.yml. nginx/nginx-dav-ext-module-3.0.0.tar.gz and nginx/ngx_http_hmac_secure_link_module-0.3.tar.gz are still listed. Can they be removed?

[kathap]

Should we add somewhere a note for operators? A migration note?
Any deployment with an explicit blobstore_type: webdav will:
- at the manifest level: blobstore_type: webdav still renders fine, but
- at CC boot: hit #5480's new raise "Unknown blobstore type: "webdav"" and fail to start.

[kathap]

Are the jobs/cloud_controller_ng/templates/blobstore_waiter.sh.erb files and calls of wait_for_blobstore still needed?

[stephanme]

The blobstore job is still needed by cf-deployment for the singleton-blobstore (webdav, batteries included). But it is now accessed via storage-cli and not anymore by the webdav blobstore provider.

See https://github.com/cloudfoundry/cf-deployment/blob/v60.8.0/cf-deployment.yml#L774-L789

[kathap]

jobs/blobstore/monit still references the removed url_signer process

[kathap]

The PR deletes spec/blobstore/backup_spec.rb and restore_spec.rb, but backup.erb / restore.erb (bin/bbr/backup, bin/bbr/restore) are still shipped and still mapped in jobs/blobstore/spec. Should they stay in?