Refine ANSI error messages and remove 'To return NULL instead'

Proposal: remove ‘To return NULL instead’ as this should not be the purpose and the user may not even aware it was returning NULLs.

Example:

Old:
1[MAP_KEY_DOES_NOT_EXIST] Key 3 does not exist. To return NULL instead, use `try_element_at`. If necessary set "spark.sql.ansi.enabled" to "false" to bypass this error.2== SQL(line 1, position 8) ==3SELECT m[3] FROM VALUES(map(1, 'Hello', 2, ...4 ^^^^
Proposed:
1[MAP_KEY_DOES_NOT_EXIST] Key 3 does not exist in the map. Use `try_element_at` to tolerate a non-existent key and return NULL. If necessary set "spark.sql.ansi.enabled" to "false" to bypass this error.2== SQL(line 1, position 8) ==3SELECT m[3] FROM VALUES(map(1, 'Hello', 2, ...4 ^^^^