bugfix: Fix claims pallet

[shekohex]

Summary of changes
Changes introduced in this pull request:

• Update encoding for MultiAddress accounts (now we match over the type and only encode the inner value)
• Fix polkadotjs message format, by adding the prefix and suffix.

Notes
I did provide two examples for claims in both Native accounts and EVM accounts

• claim using EVM: https://gist.github.com/shekohex/6af3f02c3099bb031f8d952376904d9f
• claim using Native: https://gist.github.com/shekohex/8a1f3088a6df88275312bc30905c2ba0

cc @AtelyPham Lmk if you will need help integrating the new format. but the tl;dr is that we now do not need the codecPrefix (i.e 0x30313031). Long version look into the diff.

Reference issue to close (if applicable)

Closes #393

[drewstone]

Deduplicate code pls @shekohex

[shekohex]

Do not merge this one yet, until @AtelyPham confirms it works for him too on the dApp. I've tested it Locally with the mentioned scripts.