fix: make amino msg name consistent across all modules (#77)

## Description

Following Cosmos SDK's convention, this PR changes amino message names
in `*.proto` files to `milkyway/{moduleName}/{messageName}` format and
names in `codec.go` files to `milkyway/{messageName}` unless the message
is `MsgUpdateParams`. This difference is because there's a 39-characters
limit on amino message name that can be used with `RegisterAminoMsg`.
Cosmos SDK does the same and sometimes it uses abbreviations such as
`cosmos-sdk/distr/MsgDepositValRewards` to work around with this limit.

Closes: MILK-56

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### Author Checklist

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not applicable and
please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type
prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json)
in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR
Targeting](https://github.com/milkyway-labs/milkyway/blob/master/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building
modules](https://docs.cosmos.network/v0.44/building-modules/intro.html)
- [ ] included the necessary unit and integration
[tests](https://github.com/milkyway-labs/milkyway/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go
code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

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I have...

- [ ] confirmed the correct [type
prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json)
in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)