feat(web-client): add iterator-based forEachMapEntry for memory-efficient storage map iteration

[swarna1101]

• Avoids allocating entire map into memory (O(1) vs O(n))
• Keep getMapEntries for backward compatibility with warning
• Add test coverage comparing both approaches

Releated to #1369

[swarna1101]

hi @igamigo @mmagician , can you pls check this

[mmagician]

@swarna1101 this is on our backlog, we're currently reviewing multiple larger PRs across the Miden repos. Thanks for your patience.