[react] context generation for contract client instances

We need some helpers to create contexts/providers for the client instances.

A good example of the client here:
https://github.com/EquilibriumEtf/frontend/blob/53e24aa7992bdaad85ec2a7c02a2e604a2d40897/client/core/index.ts#L27
https://gist.github.com/pyramation/05cebb95208accbcc76fbbe273211167

example of provider here:
https://github.com/EquilibriumEtf/frontend/blob/53e24aa7992bdaad85ec2a7c02a2e604a2d40897/client/react/client/EquilibriumProvider.tsx#L8
https://gist.github.com/pyramation/9db71d59e66694160d1194d291355c04

With a few changes:

- [ ] instead of all instances in one massive context, potentially have context for each client
- [ ] instead of wallet data, potentially just use `address: string` or whatever data is required

Start by reviewing the linked client example at client/core/index.ts and the provider example at client/react/client/EquilibriumProvider.tsx, along with the two gists. Determine the intended context and provider API for each client instance, then confirm that the implementation supports the requested client-specific contexts and required address or wallet data.

索引モデルが issue の本文から書いたものです。