Ambiguity in modules regarding the type Height

[adizere]

Summary of Bug

There are currently two type declarations for Height in the modules:

1. A general definition at the top-level of modules:

https://github.com/informalsystems/ibc-rs/blob/65487863a68e6307d1b08c02f202a4ba1f2c6340/modules/src/lib.rs#L36

2. Then the Height being used in each specific module is different, for example:

https://github.com/informalsystems/ibc-rs/blob/c447e63692c663a6af325196e8f92cf9a32bf91d/modules/src/ics03_connection/events.rs#L11-L14

Both types are imported from tendermint (one from the light the other from block) and both boil down to a u64. Unless there is a specific reason to keep both, we should be consistent here. Even better, maybe we can have our own definition of a Height that is (in some sense) even more general than the definitions from tendermint.

Version

Steps to Reproduce

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