Optimize Hasblock

[terencechain]

We often check a validity of an object by whether the corresponding block has been processed. The naive way is to check block exists in DB. Another less known way is check if the block exists in fork choice store. Check fork choice store is ~10x faster than DB:

BenchmarkHasBlockDB-12                   2767405               381 ns/op
BenchmarkHasBlockForkChoiceStore-12     23765187                40.0 ns/op

This implements hasBlock which checks fork choice store first then check DB

[codecov]

Codecov Report

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The diff coverage is 39.17%.

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