move NewBatchFuture API to stable workflow package (#1459)

Signed-off-by: Shijie Sheng <liouvetren@gmail.com>

Detailed Description
Move NewBatchFuture API out of X package.

Impact Analysis

Backward Compatibility: breaking for x package users. This is expected since it's experimental feature
Forward Compatibility: not applicable since it's a pure client side feature
Testing Plan

Unit Tests: Yes but not for this pure package change particularly.
Persistence Tests: no applicable
Integration Tests: we have
Compatibility Tests: it's an intended breaking change
Rollout Plan

What is the rollout plan? Existing users will need to make code changes after upgrading it.
Does the order of deployment matter? No
Is it safe to rollback? Does the order of rollback matter? Yes. No
Is there a kill switch to mitigate the impact immediately? Not needed

Author: shijiesheng

x/batch.go renamed to workflow/batch.go

@@ -1,11 +1,10 @@
-package x
+package workflow
 
 import (
 	"go.uber.org/cadence/internal/batch"
-	"go.uber.org/cadence/workflow"
 )
 
-var _ workflow.Future = (BatchFuture)(nil) // to ensure it's compatible
+var _ Future = (BatchFuture)(nil) // to ensure it's compatible
 
 // BatchFuture wraps a collection of futures, and provides some convenience methods for dealing with them in bulk.
 type BatchFuture interface {
@@ -22,10 +21,10 @@ type BatchFuture interface {
 	// exposed normally, but multiple ones are bundled in the same way as errors.Join.
 	// For consistency when checking individual errors, consider using `multierr.Errors(err)` in all cases,
 	// or `GetFutures()[i].Get(ctx, nil)` to get the original errors at each index.
-	Get(ctx workflow.Context, valuePtr interface{}) error
+	Get(ctx Context, valuePtr interface{}) error
 	// GetFutures returns a slice of all the wrapped futures.
 	// This slice MUST NOT be modified, but the individual futures can be used normally.
-	GetFutures() []workflow.Future
+	GetFutures() []Future
 }
 
 // NewBatchFuture creates a bounded-concurrency helper for doing bulk work in your workflow.
@@ -35,6 +34,6 @@ type BatchFuture interface {
 //
 // When NewBatchFuture is called, futures created by the factories will be started concurrently until the concurrency limit (batchSize) is reached.
 // The remaining factories will be queued and started as previous futures complete, maintaining the specified concurrency level.
-func NewBatchFuture(ctx workflow.Context, batchSize int, factories []func(ctx workflow.Context) workflow.Future) (BatchFuture, error) {
+func NewBatchFuture(ctx Context, batchSize int, factories []func(ctx Context) Future) (BatchFuture, error) {
 	return batch.NewBatchFuture(ctx, batchSize, factories)
 }