fix(x/bank): Better handling of negative spendable balances (backport #21407)

[mergify]

Description

This PR fixes a few things related to spendable balances.

1. Fix the SpendableCoins keeper method to return all positive balances instead of returning zero when one denom has more locked than available. Before this PR, if someone had 10denoma and 15denomb, but had 11denoma locked, this method would return an empty Coins even though there's actually 15denomb that they could spend. After this PR, it'd return that 15denomb.
2. Fix the SpendableCoin keeper method to report zero spendable if there's more locked than available for that denom. Before this PR, if there were more locked than available, this method would return a negative coin. In the SDK, the only place this method is used is in the SpendableBalanceByDenom query, so the SDK didn't have any further bugs here, but there could easily be such bugs in other chains.
3. Fix pagination of the SpendableBalances query. Before this PR, it was using the pagination stuff to identify which denoms to include in the results, then calling the SpendableCoins keeper method to get the amounts. But that keeper method calls GetAllBalances and gets the balances of all denoms anyway, defeating the purpose of the pagination. With this PR, it only gets the page of balances and reduces each by their locked amounts.
4. Fixes the SpendableBalances query so that it returns the correct amounts when an account has one or more denoms with more locked than available. Before this PR, if an account had an amount of two denoms, but has more locked than available for one of them, this query would return two zero-coin entries, one for each denom. After this PR, it'll return a zero-coin entry just for the one denom, and the actual spendable amount for the other.

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Summary by CodeRabbit

• New Features

  • Enhanced validation for coin transactions with improved checks on send restrictions.
  • Updated logic for calculating spendable balances, accounting for locked coins.

• Bug Fixes

  • Resolved issues with the accuracy of spendable balances, ensuring correct reporting even with locked coins.
  • Fixed the SpendableCoins method to return only positive spendable balances.

• Tests

  • Added new test cases to validate functionality for multiple accounts in the bank module.

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This is an automatic backport of pull request #21407 done by [Mergify](https://mergify.com).

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