Executor cachePrefix does not account for multiple servers

Problem/Motivation

I've got multiple GraphQL servers setup.

After the cache is primed, I get back the cache of another server when querying.

This flows through to nearly any query. Running the same query on multiple servers returns whatever was cached first, from the first service's query.

Steps to reproduce

- Create Server A
- Create Server B

Each server should have a different configuration, leading to a different schema. Do this however you see fit? For me, with GraphQL Compose, I setup a different config per service.

- Visit voyager for Server A, see correct result
- Visit voyager for Server B, see Server A's introspective data.

Proposed resolution

src/GraphQL/Execution/Executor.php
cachePrefix() method

Add the Server ID to the sha256 hash:

 'server_id' => $this->context->getServer()->id(),

Remaining tasks

User interface changes

API changes

Data model changes