schema-accounts: Add new SDK module to manage account based schema

[vatsa287]

• Add new package schema-accounts to have capability of creation of schema based out of accounts.
• Update the schema-model regex to handle newer identifiers.
• Integrate the schema-accounts with registries, i.e handling the existence of schemaUri etc.
• Demo script updates to demonstrate above.

[vatsa287]

@amarts PTAL

[amarts]

I have some further thoughts on how we can merge and use schema pallet get both account and DID. But for now, this is a progress compared to earlier, so lets keep that enhancements to next versions.