perf: improve query when no enough memory cache

[hengfeiyang]

We have some environments to control the memory cache:

option	default value	description
ZO_MEMORY_CACHE_ENABLED	true	you can disable memory cache, default is enable
ZO_MEMORY_CACHE_CACHE_LATEST_FILES	false	you can auto cache the latest files for accelerate query, default is false, this need more memory
ZO_MEMORY_CACHE_MAX_SIZE	30%	default use 30% of total memory, you can configure it by a value (MB)

And if a query needs to load parquet files more than 30% of total memory cache, the query will skip memory cache.

For example:

I have 500MB memory cache.

• a query needs to load 100MB parquet files, ok, let's use the memory cache.
• a query needs to load >250MB parquet files, ok, too big, directly load files from storage. disk / s3.

[hengfeiyang]

fix #312