better way to one-shot query storage

[shunjizhan]

• I'm submitting a ...

• Bug report
• Feature request
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• What is the current behavior and expected behavior?

When querying storage for historical blocks, we need to decorate a whole apitAt object with await api.at(blockHash). However, if we only need to one-shot query for storage for a certain block, there will be a lot of wasted resources decorating api.*.

As a result, if we need to query storage for a lot of blocks (not simultaneously, but at high frequency), this will cause significant performance issue.

Can we have a more efficient way to query one-shot storage, such as await api.queryAt(blockHash).section.method()? In this way, we know it's only querying storage so can skip other unnecessary decoration.

For multiple queries among api.* for the same block, we can still use apiAt(blockHash)