Set the capability bit for worker heartbeat in NamespaceInfo.

 SDK will use this to determine whether to send heartbeat or not.

- [ ] built
- [ ] run locally and tested manually
- [ ] covered by existing tests
- [x] added new unit test(s)
- [ ] added new functional test(s)

None. Feature not yet enabled in prod.

## What changed?
- Set default priority on all internalTasks after creation.
- Combine effective priority and poll forwarder flag into one value.
- For simplicity, default priority and level count are set at partition
load time.

## Why?
Tasks with unset priority key were not actually getting the default
value when read from backlog. This sets the default priority on all
sync, backlog, query, and nexus tasks. (Priority is not meaningful for
sync match tasks, and nexus has no priority yet, but they're set anyway
for consistency.) This will also make it easier to adjust the priority
for other purposes, e.g. prioritizing the old backlog for migrating
persistence.

## How did you test it?
- [x] built
- [x] run locally and tested manually
- [x] covered by existing tests
- [ ] added new unit test(s)
- [x] modified functional test

… version stamp (#8488)

## What changed?
Do not set `SourceVersionStamp` on new workflow execution when a v3
versioned workflow retries.

## Why?
If the `SourceVersionStamp` is set, the retried workflow will be treated
as a non-v3-versioned workflow and won't be processed by v3 versioned
workers.

## How did you test it?
- [x] built
- [ ] run locally and tested manually
- [ ] covered by existing tests
- [ ] added new unit test(s)
- [x] added new functional test(s)


<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Prevents v3-versioned workflow retries from inheriting a deprecated
version stamp, clones `VersioningInfo` in describe response, and adds
functional tests covering retry inheritance scenarios.
> 
> - **History API/Workflow**:
> - **Retry logic**: Only set `SourceVersionStamp` when previous run's
versioning behavior is `UNSPECIFIED` (legacy), avoiding stamp on
v3-versioned retries.
> - **DescribeWorkflow**: Safely clone `VersioningInfo`
(`common.CloneProto`) in `WorkflowExecutionInfo` to avoid mutation
issues during marshalling.
> - **Tests**:
> - Add `Versioning3Suite` retry tests: pinned/unpinned, retry of child
and continue-as-new, asserting inherit vs no-inherit and behavior
(`PINNED` vs `AUTO_UPGRADE`).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
a36246e. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->