Fix column name with special character when create materialized view

[dai-chen]

Description

Spark StructType.fromDDL() requires all columns quoted if any special character. Previously all table/index/column names after Flint parser has been unquoted. Quote them before calling fromDDL method and finally it is unquoted in OpenSearch doc as before.

Reproducing the bug

CREATE MATERIALIZED VIEW test
AS
SELECT startTime AS `start.time`
...

start.time string not null,count long not null
----^^^

at org.apache.spark.sql.catalyst.parser.ParseException.withCommand(ParseDriver.scala:306)
at org.apache.spark.sql.catalyst.parser.AbstractSqlParser.parse(ParseDriver.scala:143)
at org.apache.spark.sql.catalyst.parser.AbstractSqlParser.parseTableSchema(ParseDriver.scala:76)
at org.apache.spark.sql.types.StructType$.fromDDL(StructType.scala:543)
at org.opensearch.flint.spark.FlintSparkIndex$.generateSchemaJSON(FlintSparkIndex.scala:143
at org.opensearch.flint.spark.mv.FlintSparkMaterializedView.metadata(FlintSparkMaterializedView.scala:58)
   ...

Issues Resolved

#84

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