…ereum#31079)

This PR is #1 of a 3-part series that implements the new log index
intended to replace core/bloombits.
Replaces ethereum#30370

This part implements the new data structure, the log index generator and
the search logic. This PR has most of the complexity but it does not
affect any existing code yet so maybe it is easier to review separately.

FilterMaps data structure explanation:
https://gist.github.com/zsfelfoldi/a60795f9da7ae6422f28c7a34e02a07e

Log index generator code overview:
https://gist.github.com/zsfelfoldi/97105dff0b1a4f5ed557924a24b9b9e7

Search pattern matcher code overview:
https://gist.github.com/zsfelfoldi/5981735641c956afb18065e84f8aff34

Note that the possibility of a tree hashing scheme and remote proof
protocol are mentioned in the documents above but they are not exactly
specified yet. These specs are WIP and will be finalized after the local
log indexer/filter code is finalized and merged.

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Co-authored-by: Felix Lange <[email protected]>