Allow schema caching per server when using a common base schema

[darvanen]

I am NOT by any means suggesting this at the fix approach, it merely shows where the problem lies so a discussion can be had regarding how to fix it.
Updated to a viable patch, though there are other ways we could approach it.

[darvanen]

See #1223 for initial notes

[darvanen]

I'm sorry, I went to try and create a test to demonstrate this but it's completely beyond me.

[darvanen]

Ok, now this PR contains a potential fix using a setter on the plugin to provide the server ID.

We could probably also do it by putting another key on the configuration that gets passed to the plugin but this seemed safer to me.

[darvanen]

Alright I give up. The last test failure is a conflict between PHPStan and phpcs

PHPStan:

 ------ ------------------------------------------------------------------ 
  Line   src/Plugin/SchemaPluginInterface.php                              
 ------ ------------------------------------------------------------------ 
  23     PHPDoc tag @param has invalid value (string                       
           The machine name of the server using this plugin.): Unexpected  
         token "\n   * ", expected variable at offset 84                   
 ------ ------------------------------------------------------------------ 

phpcs:

FILE: ...odules/graphql/src/Plugin/GraphQL/Schema/SdlSchemaPluginBase.php
----------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
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 47 | ERROR | [x] Do not append variable name "$serverId" to the type
    |       |     declaration in a member variable comment
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PHPCBF CAN FIX THE 1 MARKED SNIFF VIOLATIONS AUTOMATICALLY
----------------------------------------------------------------------