chore!: refactore store key constructors

[robert-zaremba]

Description

Follow up on #1573
Cleanup store key prefix functions.

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Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• added appropriate labels to the PR
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• 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)

[rbajollari]

👍

[gsk967]

LGTM

[toteki]

Hold on before merging this - I want to test it against mainnet store

[codecov-commenter]

Codecov Report

Merging #1578 (022b9e7) into main (56b89e0) will increase coverage by 0.38%.
The diff coverage is 94.64%.

@@            Coverage Diff             @@
##             main    #1578      +/-   ##
==========================================
+ Coverage   52.08%   52.47%   +0.38%     
==========================================
  Files          72       73       +1     
  Lines        7092     7040      -52     
==========================================
  Hits         3694     3694              
+ Misses       3125     3073      -52     
  Partials      273      273              

Impacted Files	Coverage Δ
x/oracle/types/keys.go	60.00% <71.42%> (+17.89%)	⬆️
util/bytes.go	100.00% <100.00%> (ø)
x/leverage/keeper/invariants.go	72.64% <100.00%> (-0.46%)	⬇️
x/leverage/keeper/iter.go	54.08% <100.00%> (ø)
x/leverage/keeper/store.go	65.58% <100.00%> (-0.66%)	⬇️
x/leverage/keeper/token.go	76.00% <100.00%> (ø)
x/leverage/types/keys.go	100.00% <100.00%> (+47.61%)	⬆️
x/oracle/keeper/historic_price.go	93.93% <100.00%> (+0.12%)	⬆️
x/oracle/keeper/keeper.go	84.79% <100.00%> (ø)

[toteki]

Looks good - also I added some leverage key_test.go cases.

[robert-zaremba]

Looks good - also I added some leverage key_test.go cases.

Thank you.