Eth2Client: improvements, refactoring (#882)

Refactor the eth2 light client to resolve an issue of missing finality for more than 5 epochs.

- Added two modes `SubmitLightClientUpdate` and `SubmitHeader`.
- By default, the client is in `SubmitLightClientUpdate` and it turns into `SubmitHeader` after submitting a light client update.
- Added integration tests for migration logic.
- The relayer can submit a `LightClientUpdate` after any number of epochs/blocks, but those can be finalized only if the size of the gap between the current finalized block and the subsequent finalized block is higher than `hashes_gc_threshold`, otherwise, the `GC` can't be applied correctly.
- Update Eth2-to-Near relay and `eth2near` crates to v0.3.0.
- Update dependencies.
- Update tests and remove irrelevant tests.

---------

Co-authored-by: Olga Kunyavskaya <olga.kunyavskaya@aurora.dev>
Co-authored-by: Kirill <kirill@aurora.dev>

contracts/near/eth2-client/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "eth2-client"
-version = "0.2.0"
+version = "0.3.0"
 authors = ["Aurora <hello@aurora.dev>"]
 edition = "2021"
 

contracts/near/eth2-client/src/data/.gitattributes

@@ -1 +1,2 @@
 *.json filter=lfs diff=lfs merge=lfs -text
+*.wasm filter=lfs diff=lfs merge=lfs -text