This PR fixes two bugs when matching attributes within events:

• When multiple events match in the same transaction or block, the query would return multiple times the same result.
• When the query contains a height range and another range, the height range would get ignored under certain conditions.
• A query containing both a height range and height equality would process them both. Now the equality is ignored when a range exists.
• Queries containing CONTAINS and EXISTS would ignore the height requirement when match.events = 1.

There have been minor improvements to the readability of the code:

• As we need to know the height range or the requested height to match events at and both whether the height related conditions are the only ones (beside match.events), there is now a heightInfo struct that encapsulates all of that. Additionally, spuradious checks on whether the length of the conditions is a certain number has been replaced with simple bool flags which are derived within the dedupHeight method.