Add show and desc materialized view SQL support

[dai-chen]

Description

1. Add SHOW/DESC materialized view SQL statement
2. Fix a bug that underlying OS exception thrown when describeIndexes() doesn't find any matched index

Documentation

https://github.com/dai-chen/opensearch-spark/blob/add-mv-show-desc-statement/docs/index.md#materialized-view

Example

SHOW MATERIALIZED VIEWS IN myglue;
myglue.default.http_logs_metrics
myglue.default.lineitem_metrics

spark-sql> DESC MATERIALIZED VIEW myglue.default.http_logs_metrics;
startTime	timestamp
count	long

Issues Resolved

#25

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