[SPARK-28581][SQL] Replace _FUNC_ in UDF ExpressionInfo

[wangyum]

What changes were proposed in this pull request?

This PR moves replaceFunctionName(usage: String, functionName: String)
from DescribeFunctionCommand to ExpressionInfo in order to make ExpressionInfo returns actual name instead of placeholder. We can get ExpressionInfos directly through SessionCatalog.lookupFunctionInfo API and get the real names.

How was this patch tested?

unit tests

[juliuszsompolski]

👍 from me.
cc @gatorsmile

[dongjoon-hyun]

Hi, @wangyum and @juliuszsompolski .
I know this comes from #25252 . However, JIRA and PR should be self-describing. This will be a commit log. Could you add the reason why we need this to the followings?

• This JIRA (https://issues.apache.org/jira/browse/SPARK-28581)
• This PR description

[SparkQA]

Test build #108469 has finished for PR 25314 at commit a5f31e3.

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

[dongjoon-hyun]

+1, LGTM. I updated the PR description and JIRA description.
Merged to master.