Remove unnecessary prefix / suffix in store keys

[robert-zaremba]

In #1578 we cleaned up store key constructors.
Various key have unnecessary length prefix or null terminator. Both are not needed if it is the last and ultimate part of the key.
Example: https://github.com/umee-network/umee/pull/1578/files#diff-b3ff0f6b42fcc3132cbb1a0210e624410a4e1ca4c7027c70928edad4ca1880baR38

It's nice to have, and we need to guarantee that the keys won't be extended.

[robert-zaremba]

up

[robert-zaremba]

@zarazan or @rbajollari do you think you can handle this?

[toteki]

If the keys are currently working and consistent with each other, we should avoid unnecessary changes due to

• requiring store migrations (delete old, add new, for all stored values)
• unintentionally introducing bugs (removing a null terminator from a prefix | denom | 0x00 could cause hypothetical denom uumee2 to be caught up in iterators over uumee if there was one) - of course no bugs would be introduced if we migrated everything perfectly, but I see no reason to create the possibility

TLDR avoid unnecessary changes