Stream async job warnings as they arrive for delete commands

[johha]

Description of the Change

cf delete, cf delete-org, and cf delete-space kick off an asynchronous Cloud Controller job and then poll it to completion. Previously the CLI aggregated every warning returned across all poll ticks and dumped them at the very end, after the job reached a terminal state. Because Cloud Controller re-sends the same warnings on every poll, a single warning could be printed dozens of times.

This PR migrates those three commands from the aggregated CloudControllerClient.PollJob path to a streaming poll: the actor returns a chan PollJobEvent (via PollJobToEventStream) that command/v7/shared.WaitForResult drains, printing warnings as they arrive instead of at the end.

Key changes:

• Streaming actors - DeleteApplicationByNameAndSpace, DeleteOrganization, and DeleteSpace now return (chan PollJobEvent, Warnings, error). For cf delete -r, the app-delete job and each route-delete job are merged into a single stream in the actor, so the whole operation streams through one channel.
• Run-scoped warning dedup - WaitForResult prints each distinct warning at most once per operation, collapsing the tick-by-tick repeats (including warnings that interleave across ticks).
• The "Waiting for the operation to complete" banner now ends with a newline so streamed warnings and progress dots start on their own line.

Example: cf delete-org against a job that returns warnings on every poll

Before (warnings aggregated and repeated per poll tick):

$ cf delete-org my-org -f
Deleting org my-org as admin...
Deletion of service instance my-db is in progress.
Deletion of service instance my-db is in progress.
Endpoint deprecated: use the /v3 API instead.
Deletion of service instance my-db is in progress.
Endpoint deprecated: use the /v3 API instead.
... (repeats per poll tick for the same few warnings) ...
OK

After (each distinct warning shown once, streamed live with progress dots):

$ cf delete-org my-org -f
Deleting org my-org as admin...
Waiting for the operation to complete
Deletion of service instance my-db is in progress.
.Endpoint deprecated: use the /v3 API instead.
....Service broker returned a warning: quota not fully reclaimed.
.....

OK

cf delete APP -r (delete app + mapped routes) and cf delete-space behave the same way - warnings from the app job and each route/space job stream through as the jobs progress.

Why Is This PR Valuable?

Users deleting orgs, spaces, or apps get feedback while the operation runs rather than a wall of duplicated text at the end. Warnings that Cloud Controller emits mid-operation (progress hints, content warnings) now surface promptly and legibly - each distinct message once - instead of being buffered until the job finishes or the poll window times out.

This is part of the ongoing effort to make recursive/async delete operations more intuitive (cloudfoundry/cloud_controller_ng#3589). The corresponding Cloud Controller work that emits these async-delete warnings is landing on the server side; this PR is the CLI half that surfaces them well.

Applicable Issues

• Related: Make recursive delete operations more intuitive cloud_controller_ng#3589 - Make recursive delete operations more intuitive

How Urgent Is The Change?

Not urgent

Other Relevant Parties

None.

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This PR was drafted with the help of Claude (Opus).

[johha]

Backport for v8: #3860