[SPARK-35798][SQL] Fix SparkPlan.sqlContext usage

[peter-toth]

What changes were proposed in this pull request?

There might be SparkPlan nodes where canonicalization on executor side can cause issues. This is a follow-up fix to conversation https://github.com/apache/spark/pull/32885/files#r651019687.

Why are the changes needed?

To avoid potential NPEs when canonicalization happens on executors.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Existing UTs.

[peter-toth]

cc @cloud-fan

[SparkQA]

Kubernetes integration test starting
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/44447/

[SparkQA]

Kubernetes integration test status success
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/44447/

[cloud-fan]

thanks for the cleanup! merging to master

[SparkQA]

Test build #139919 has finished for PR 32947 at commit 6caeef1.

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

[peter-toth]

Thanks for the review.

[HyukjinKwon]

Nice!