Introduce LightBlock support for MockContext

[adizere]

Overview

Closes cosmos/ibc-rs#100

Description

This PR introduces two important changes:

1. Module mock_context.rs was expanded

This module was broken down into two separate modules: context.rs with an implementation of MockContext

https://github.com/informalsystems/ibc-rs/blob/110a3d81dc811820a73879fe43ce8a384f435c4a/modules/src/mock/context.rs#L31

and host.rs with various host chain-specific types, e.g., HostBlock

https://github.com/informalsystems/ibc-rs/blob/b9b4667699a2b7f3b2e95d1421389fea800b93c0/modules/src/mock/host.rs#L30-L33

Note that two types of blocks are now possible: mocks or synthetically generated Tendermint blocks (based on testgen).

2. The ibc crate now exports a mocks feature

https://github.com/informalsystems/ibc-rs/blob/b9b4667699a2b7f3b2e95d1421389fea800b93c0/modules/Cargo.toml#L17-L20

This feature grants the relayer access to mock structures, so the relayer can build an in-process mock chain based on MockContext.

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For contributor use:

• Updated the Unreleased section of CHANGELOG.md with the issue.
• If applicable: Unit tests written, added test to CI.
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Updated relevant documentation (docs/) and code comments.
• Re-reviewed Files changed in the Github PR explorer.

[codecov-io]

Codecov Report

Merging #390 (7fc7fcb) into master (b1b37f5) will increase coverage by 20.9%.
The diff coverage is 66.6%.

@@            Coverage Diff            @@
##           master    informalsystems/hermes#390      +/-   ##
=========================================
+ Coverage    13.6%   34.6%   +20.9%     
=========================================
  Files          69     155      +86     
  Lines        3752   10456    +6704     
  Branches     1374    3852    +2478     
=========================================
+ Hits          513    3621    +3108     
- Misses       2618    6213    +3595     
- Partials      621     622       +1     

Impacted Files	Coverage Δ
modules/src/events.rs	0.0% <0.0%> (ø)
modules/src/ics02_client/events.rs	0.0% <ø> (ø)
modules/src/ics02_client/msgs.rs	0.0% <0.0%> (ø)
modules/src/ics02_client/raw.rs	0.0% <0.0%> (ø)
modules/src/ics03_connection/error.rs	13.6% <0.0%> (-19.7%)	⬇️
modules/src/ics04_channel/error.rs	75.0% <ø> (+50.0%)	⬆️
modules/src/ics04_channel/msgs/acknowledgement.rs	0.0% <0.0%> (ø)
modules/src/ics04_channel/msgs/chan_open_try.rs	66.8% <ø> (ø)
modules/src/ics04_channel/msgs/recv_packet.rs	0.0% <ø> (ø)
modules/src/ics04_channel/msgs/timeout.rs	0.0% <ø> (ø)
... and 288 more

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[ancazamfir]

Suggested change

	HostType::Mock,
	HostType::SynteticTendermint,

It would be good to create different types of contexts in the test. I think there are a few places where the code still needs to be updated, e.g. with_client_parametrized() or store_client_state().

[adizere]

Modified context ctx_b to rely on a HostType::SynteticTendermint chain and updated the relevant parts.

Note that some verification functions (like this one) are incomplete, but will add more checks in there as we go along and write new tests.

[ancazamfir]

Very cool! The first time that we have different chains and client types