[Docs] Update "Adding On-Chain Module Parameters" (#839)

## Summary

Updates "Adding On-Chain Module Parameters" doc to:
1. Reflect recent changes in param update testing (see: #826)
2. Group related steps
3. Improve consistency between and readability of code snippets
4. Fill in gaps:
  - Omitted steps/files.
- Adding individual param updates (`MsgUpdateParam`) to a module which
doesn't already support it.


## Issue

- #612 
- #826 

## Type of change

Select one or more from the following:

- [ ] New feature, functionality or library
- [ ] Consensus breaking; add the `consensus-breaking` label if so. See
#791 for details
- [ ] Bug fix
- [ ] Code health or cleanup
- [x] Documentation
- [ ] Other (specify)

## Testing

- [x] **Documentation**: `make docusaurus_start`; only needed if you
make doc changes
- [ ] **Unit Tests**: `make go_develop_and_test`
- [ ] **LocalNet E2E Tests**: `make test_e2e`
- [ ] **DevNet E2E Tests**: Add the `devnet-test-e2e` label to the PR.

## Sanity Checklist

- [ ] I have tested my changes using the available tooling
- [ ] I have commented my code
- [ ] I have performed a self-review of my own code; both comments &
source code
- [ ] I create and reference any new tickets, if applicable
- [ ] I have left TODOs throughout the codebase, if applicable

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Co-authored-by: red-0ne <[email protected]>
Co-authored-by: Daniel Olshansky <[email protected]>