Migrate all control handling logics to AsyncRPC and cleanup Amber - #1000

…ache#1000)

On high level, this PR:

1. made `workerlayer`, `opexecconfig`, `linkstrategy`, `workflow` object more usable and they contain mutable state information now.
2. rewrote all the control handling logic to asyncRPC
3. reworked `WorkflowPartialCompleted` mechanism. now workers will send `LinkCompleted` message whenever the receiver of a link receives all the data from the senders of that link. 
4. replaced all `AmberTag` to `VirtualIdentity`, now `VirtualIdentity` is the only identifier we use in the code.
5. codebase cleanup.
After the merge of this PR, the major refactoring effort of Amber is DONE in my opinion. (I would like to call it the Amber2.0 now)

…#8396)

### What changes were proposed in this PR?

Deletes `MockKillWorkerResource.scala`, a file whose every non-blank
line after the ASF header is a comment — the commented-out remains of a
JAX-RS `/kill/worker` endpoint — together with the commented-out Jersey
registration line in `TexeraWebApplication` that pointed at it. Pure
deletion, no behaviour change: **−40 lines**, none of them compiled.

### History

| | |
| --- | --- |
| **Introduced by** | the initial amber import, commit `41a8a92017`
(2020-08-20) — predates the PR workflow — which also registered it live
with Jersey |
| **Disabled by** | apache#1000 (`4a64935c35`, 2021-01-30) — "Migrate all
control handling logics to AsyncRPC and cleanup Amber" commented out the
registration line and the whole file body in the same diff. Nothing has
compiled from the file since |

Registered live for about five months, 2020-08-20 → 2021-01-30, then
commented out for the five and a half years since. The commented
registration line goes with the file.

### Any related issues, documentation, discussions?

Closes apache#8393

### How was this PR tested?

Existing tests only — no spec referenced it.

Locally, from the repo root with Java 17:

- `sbt "WorkflowExecutionService/Test/compile"` — success.
- `sbt scalafmtCheckAll "scalafixAll --check"` — clean.

Verification, re-runnable by a reviewer:

```
git grep -n MockKillWorkerResource                # nothing left on this branch; on main, two hits: the file and the commented registration line
git grep -n "jersey.register" -- amber/src/main   # the live registrations, untouched
```

### Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Claude Opus 5, Claude Fable 5.1)