[SPARK-14225][SQL] Cap the length of toCommentSafeString at 128 chars

## What changes were proposed in this pull request?

Builds on https://github.com/apache/spark/pull/12022 and (a) appends "..." to truncated comment strings and (b) fixes indentation in lines after the commented strings if they happen to have a `(`, `{`, `)` or `}`

## How was this patch tested?

Manually examined the generated code.

Author: Sameer Agarwal <sameer@databricks.com>

Closes #12044 from sameeragarwal/comment.