perf(multichain-account-service): add Solana account batching

[ccharly]

Explanation

Implementing proper batching for our Solana account provider.

References

• perf(multichain-account-service): add :createMultichainAccountGroups action to batch account creation  #7801
• perf(account-tree-controller): use batched account creation in backup & sync #7907

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
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them