Optimization statements performance related to system meta data

[Benjamin2037]

Feature Request

Is your feature request related to a problem? Please describe:

This issue will optimize the query performance for metadata-related statements

Scenario1:

SELECT column_name 
FROM information_schema.statistics
WHERE index_name = 'PRIMARY'
 AND table_schema = database()   
 AND table_name = 'xx' 
 ORDER BY seq_in_index;

Scenario2:

SELECT table_comment 
FROM information_schema.tables 
WHERE table_schema = database() AND table_name = 'xxx'

Scenario3:

SELECT table_name 
FROM information_schema.tables 
WHERE table_schema = database() AND table_type = 'xxx'

Describe the feature you'd like:

Speed up the query for metadata to be executed more quickly.

1. Push down predicates to memTableReader.
2. Do column pruning when reading infoschema.tables.

[ywqzzy]

/close as completed

[jebter]

Releted to issue: https://github.com/pingcap/tidb/issues/50959