rework query dispatch and execution - part III

[kukeiko]

What

Completely scrap the current interceptor based implementation to instead use a simpler, more predictable one.

Why

• not all hydration scenarios actually work. and to make them work, substantial changes to the interceptors would be required
• debugging is an absolute nightmare. the new implementation will also have its debugging challenges, but much less so
• the ability to delegate execution to different components based on received entities is nice, yet too complex to have for the benefit it provides. instead, we will fully plan the execution of a query before any service is contacted (think "explain" in sql terms), and then use that plan to execute the query

How

• add a new EntityQueryExecutor class that will plan a query & execute the plan (replaces current EntityQueryExecutor, or one of them is renamed)
• add some EntityQueryShape & CriterionShape functionality required to plan a query
• remove interceptors, and rework
• use linear instead of recursive execution (as it is now w/ interceptors)
• reuse EntitySourceEndpoints and adapt as needed
• reuse already established methods for the user to define their endpoints/hydrators, but adapt as needed
• repurpose EntityStream/EntityStreamPackets, but likely dropping the rejectedQueries part

Notes

• successor of #195
• some tests might need to be dropped (but ideally replaced)
• partial success identification of a query will worsen substantially, which is to be fixed in a separate issue
• this rework will focus on usage of Equals & InArray criteria only. Missing cases to be probably be implemented in a separate issue as well?

[kukeiko]

In the latest commit I've added the implementation candidate, and noted: "immediate next steps are to try out & fix some more loading/hydration scenarios" - deciding to scrap that, I know that there for sure are a few cases missing, but I am happy with what I have and want to instead go to directly moving the changes into the actual codebase.

[kukeiko]

The item got autoclosed due to last fix commit, but that is fine, as rework is complete :)

[kukeiko]

last two commits were supposed to be for #219, whoopsie