refactor: update account group name uniqueness checks

[PatrykLucka]

Explanation

This PR changes the account groupc uniqueness checks to validate uniqueness only within the same wallet, allowing duplicates between wallets.

References

Jira ticket: https://consensyssoftware.atlassian.net/browse/MUL-795

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

[ccharly]

Perfect! 💪