docs: add more clear and description comments

[jaybxyz]

Description

closes: #51

Tasks

• scan through client folder to improve comments
• scan through keeper folder to improve comments
• scan through simulation folder to improve comments (work will be done in test: randomize simulations for edge cases #32)
• scan through types folder to improve comments
• Make proto-all, Update published swagger on swaggerHub

---

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.

• Appropriate labels applied
• Targeted PR against correct branch
• 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
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[jaybxyz]

@hallazzang I added/updated comments in both keeper and types packages. Can you review those whenever you can? There is TODO comment in BudgetCollection of keeper/budget.go and I am not sure if that is already done so I leave it there.

[dongsam]

LGTM,

but It seems like proto-format proto-lint proto-gen was not executed well.
This can happen if the proto docker container for another module collides even if the make is executed. let me commit this.

and Swagger was updated through this PR. The API specification is not changed but description, etc., so it is not necessary to upgrade the swagger version, but if there is a change from next time, it would be good to upgrade the swagger version from client/docs/config.json, re-generate it, and update it with the swagger hub.