[SPARK-32793][FOLLOW-UP] Minor corrections for PySpark annotations and SparkR

[zero323]

What changes were proposed in this pull request?

• Annotated return types of assert_true and raise_error as discussed here.
• Add assert_true and raise_error to SparkR NAMESPACE.
• Validating message vector size in SparkR as discussed here.

Why are the changes needed?

As discussed in review for #29947.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

• Existing tests.
• Validation of annotations using MyPy

[SparkQA]

Test build #129559 has finished for PR 29978 at commit 4da2633.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Kubernetes integration test starting
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/34165/

[SparkQA]

Kubernetes integration test status success
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/34165/

[HyukjinKwon]

Merged to master.

[zero323]

Thanks @HyukjinKwon