Fix/refacto protect data

[PierreJeanjacquot]

• type: fully type protectData and protectDataObservable
  • the dataSchema returned by protectData is now a DataSchema instead of a string to enable to type check it and make it easier to work with in TS

export type DataSchemaEntryType =
   | 'boolean'
   | 'number'
   | 'string'
   | MimeType;
 export interface DataSchema
   extends Record<string, DataSchema | DataSchemaEntryType> {}

• refacto: reuse signer and provider from iexec SDK instead of instantiating new ones
• fix: added error cases to schema extraction for unsupported type of data

[Le-Caignec]

it works perfectly with all demo.But i listed some improve may be

[Le-Caignec]

RAS