refactor: switch Int and Uint to cosmossdk.io/math (backport #481)

[mergify[bot]]

This is an automatic backport of pull request #481 done by Mergify. Cherry-pick of 15e144a1b9220c7c307e2a962a72fa2ebe6aeedf has failed:

On branch mergify/bp/v16.x/pr-481
Your branch is up to date with 'origin/v16.x'.

You are currently cherry-picking commit 15e144a1b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
    modified:   types/coin.go
    modified:   types/dec_coin.go
    modified:   types/decimal.go
    modified:   types/denom.go
    deleted:    types/int.go
    deleted:    types/int_internal_test.go
    deleted:    types/int_test.go
    new file:   types/math.go
    deleted:    types/uint.go
    deleted:    types/uint_internal_test.go
    deleted:    types/uint_test.go
    modified:   x/auth/vesting/types/vesting_account.go
    modified:   x/distribution/keeper/delegation_test.go
    modified:   x/distribution/keeper/validator.go
    modified:   x/gov/keeper/deposit.go
    modified:   x/gov/keeper/tally.go
    modified:   x/gov/simulation/operations.go
    modified:   x/slashing/handler_test.go
    modified:   x/staking/app_test.go
    modified:   x/staking/genesis_test.go
    modified:   x/staking/handler_test.go
    modified:   x/staking/keeper/delegation_test.go
    modified:   x/staking/keeper/grpc_query_test.go
    modified:   x/staking/keeper/pool.go
    modified:   x/staking/keeper/querier_test.go
    modified:   x/staking/keeper/slash.go
    modified:   x/staking/keeper/slash_test.go
    modified:   x/staking/keeper/validator_test.go
    modified:   x/staking/types/msg.go
    modified:   x/staking/types/validator.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
    both modified:   go.mod
    both modified:   go.sum

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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