[YSQL] [PERF] Use Postgres metadata for table descriptor.

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Jira Link: DB-4836
Currently YSQL has two different and separate metadata contents.

• First set of metadata is containing the actual descriptor of database objects. This is stored in Postgres system catalogs.
• Second set of metadata is containing the descriptor of the storage of the database objects. Most of the information in this second set can be derived from the first set, and the rest should be merged with the first set of metadata.
• The two sets of metadata are stored and cached separately and differently when they should have been kept together.
• The storage layer (DocDB) has no access to the first set of metadata, and therefore cannot execute any SQL operations including evaluating expressions. This project is a MUST before we can resolve [YQL] [PERF] Push down expressions and part of query plan to Proxy Server and DocDB #2040 , [YSQL] [PERF] Optimize the execution pipeline when expression evaluation is not needed in Postgres layer #2173 , and any future optimization that involves moving Postgres operations to DocDB layer.

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'cc @mbautin @m-iancu @ndeodhar