Expand on Accounts schema in GraphQL

[buffalojoec]

Making this issue to track discussions on the new Accounts schema in GraphQL.

The revised Account schema should (potentially) make use of interfaces in the following manner - as discussed in this comment:

query {
  account(address: "abc") {
    # Stuff that every account has...
    address
    owner
    space
    ... on MintAccount {
      decimals
      isInitialized
      mintAuthority
      supply
    }
  }
}

In doing so, we'll need to ensure field names don't collide. This means, for example, changing owner to ownerProgram in the root Account type.

Developers also shouldn't need to do spread syntax on nested account queries, but this will require careful consideration of encoded nested account data (base58, etc.). See this comment for more context.

[buffalojoec]

Note, this PR continues talks from #1817, since schema modifications will be much easier to follow after #1819

[github-actions]

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