[SPARK-43028][SQL] Add error class SQL_CONF_NOT_FOUND

[allisonwang-db]

What changes were proposed in this pull request?

This PR adds a new error class SQL_CONF_NOT_FOUND.

Why are the changes needed?

To make the error message more user-friendly when getting a non-existing SQL config. For example:

spark.conf.get("some.conf")

Before this PR, it will throw this error:

java.util.NoSuchElementException: some.conf

After this PR:

[SQL_CONF_NOT_FOUND] The SQL config "some.conf" cannot be found. Please verify that the config exists.

Does this PR introduce any user-facing change?

Yes. The error message will be changed.

How was this patch tested?

Added a new UT.

[MaxGekk]

Please, quote the config in the code and remove "" around the key:

Suggested change

	"The SQL config \"<key>\" cannot be found. Please verify that the config exists."
	"The SQL config <sqlConf> cannot be found. Please verify that the config exists."

[MaxGekk]

Please, quote the config using toSQLConf()

[MaxGekk]

Waiting for CI.

[allisonwang-db]

cc @srielau

[MaxGekk]

@allisonwang-db Could you fix the R test:

══ Failed ══════════════════════════════════════════════════════════════════════
── 1. Failure ('test_sparkSQL.R:3963'): Setting and getting config on SparkSessi
`sparkR.conf("completely.dummy")` threw an error with unexpected message.
Expected match: "Config 'completely.dummy' is not set"
Actual message: "Unknown error: Error in handleErrors(returnStatus, conn): org.apache.spark.SparkNoSuchElementException: 

[MaxGekk]

+1, LGTM. Merging to master.
Thank you, @allisonwang-db and @srielau for review.