feat: Add metadata field to Vote in x/gov

[likhita-809]

Description

Closes: #11268

Add metadata to Vote in x/gov using the existing maxMetadataLen constraint.

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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
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• 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 ! 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)

[codecov]

Codecov Report

Merging #11308 (03dcae4) into master (da36c46) will decrease coverage by 0.05%.
The diff coverage is 39.28%.

@@            Coverage Diff             @@
##           master   #11308      +/-   ##
==========================================
- Coverage   65.98%   65.93%   -0.06%     
==========================================
  Files         696      662      -34     
  Lines       71310    68527    -2783     
==========================================
- Hits        47055    45180    -1875     
+ Misses      21340    20702     -638     
+ Partials     2915     2645     -270     

Impacted Files	Coverage Δ
server/rollback.go	0.00% <0.00%> (ø)
store/rootmulti/store.go	73.52% <0.00%> (-2.00%)	⬇️
x/gov/client/cli/tx.go	14.28% <0.00%> (-0.61%)	⬇️
x/gov/keeper/msg_server.go	6.57% <0.00%> (ø)
x/gov/types/v1beta2/vote.go	27.27% <0.00%> (ø)
x/gov/keeper/vote.go	89.28% <50.00%> (-3.22%)	⬇️
x/gov/client/testutil/suite.go	100.00% <100.00%> (ø)
x/gov/keeper/keeper.go	77.10% <100.00%> (+1.46%)	⬆️
x/gov/keeper/proposal.go	77.97% <100.00%> (+0.13%)	⬆️
x/gov/simulation/operations.go	85.31% <100.00%> (ø)
... and 37 more

[anilcse]

Lgtm