ibc: core restructure

[fedekunze]

Description

closes: #6945

tree -L 3 x/ibc/
x/ibc/
├── applications
│   └── transfer
│       ├── client
│       ├── handler.go
│       ├── handler_test.go
│       ├── keeper
│       ├── module.go
│       ├── module_test.go
│       ├── simulation
│       ├── spec
│       └── types
├── core
│   ├── 02-client
│   │   ├── abci.go
│   │   ├── abci_test.go
│   │   ├── client
│   │   ├── doc.go
│   │   ├── genesis.go
│   │   ├── handler.go
│   │   ├── handler_test.go
│   │   ├── keeper
│   │   ├── module.go
│   │   ├── simulation
│   │   └── types
│   ├── 03-connection
│   │   ├── client
│   │   ├── genesis.go
│   │   ├── handler.go
│   │   ├── keeper
│   │   ├── module.go
│   │   ├── simulation
│   │   └── types
│   ├── 04-channel
│   │   ├── client
│   │   ├── genesis.go
│   │   ├── handler.go
│   │   ├── keeper
│   │   ├── module.go
│   │   ├── simulation
│   │   └── types
│   ├── 05-port
│   │   ├── keeper
│   │   └── types
│   ├── 23-commitment
│   │   └── types
│   ├── 24-host
│   │   ├── errors.go
│   │   ├── keys.go
│   │   ├── parse.go
│   │   ├── validate.go
│   │   └── validate_test.go
│   ├── client
│   │   ├── cli
│   │   └── query.go
│   ├── exported
│   │   ├── channel.go
│   │   ├── client.go
│   │   ├── commitment.go
│   │   └── connection.go
│   ├── genesis.go
│   ├── genesis_test.go
│   ├── handler.go
│   ├── handler_test.go
│   ├── ibc_test.go
│   ├── keeper
│   │   ├── grpc_query.go
│   │   └── keeper.go
│   ├── module.go
│   ├── simulation
│   │   ├── decoder.go
│   │   ├── decoder_test.go
│   │   ├── genesis.go
│   │   └── genesis_test.go
│   ├── spec
│   │   ├── 01_concepts.md
│   │   ├── 02_state.md
│   │   ├── 03_state_transitions.md
│   │   ├── 04_messages.md
│   │   ├── 05_callbacks.md
│   │   ├── 06_events.md
│   │   └── README.md
│   └── types
│       ├── codec.go
│       ├── genesis.go
│       ├── genesis.pb.go
│       └── query.go
├── light-clients
│   ├── 06-solomachine
│   │   ├── client
│   │   ├── doc.go
│   │   ├── module.go
│   │   ├── spec
│   │   └── types
│   ├── 07-tendermint
│   │   ├── client
│   │   ├── doc.go
│   │   ├── module.go
│   │   └── types
│   └── 09-localhost
│       ├── doc.go
│       ├── module.go
│       └── types
└── testing
    ├── chain.go
    ├── coordinator.go
    ├── mock
    │   ├── README.md
    │   ├── doc.go
    │   ├── mock.go
    │   ├── privval.go
    │   └── privval_test.go
    ├── solomachine.go
    └── types.go

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #7434 into master will increase coverage by 0.28%.
The diff coverage is 77.96%.

@@            Coverage Diff             @@
##           master    #7434      +/-   ##
==========================================
+ Coverage   54.81%   55.10%   +0.28%     
==========================================
  Files         587      588       +1     
  Lines       36512    36787     +275     
==========================================
+ Hits        20014    20270     +256     
- Misses      14406    14416      +10     
- Partials     2092     2101       +9     

[cwgoes]

(needs a rebase)

[colin-axner]

🎉 thanks for doing this @fedekunze !!