Replace QPF with QueryExecution mockable module

[l4l]

Description of the Change

QueryProcessingFactory cannot be replaced with other module, thus require more awful tests. It was replaced with QueryExecution interface and QueryExecutionImpl class (just copied previous implementation)

Benefits

QueryExecution can be mocked, simpler tests, fuzzing test are fixed (also find_fuzz is now correct)

Possible Drawbacks

Explicit mutex lock on each query

[kamilsa]

Forward declaration?

[lebdron]

One of the reasons to introduce connection pool and SOCI was to remove locks. Please remove the mutex and use a unique connection for each query from the client.

[sorabot]

SonarQube analysis reported 6 issues

1. find_fuzz.cpp#L28: Variable 'storage_' is assigned in constructor body. Consider performing initialization in initialization list.
2. find_fuzz.cpp#L29: Variable 'bq_' is assigned in constructor body. Consider performing initialization in initialization list.
3. find_fuzz.cpp#L30: Variable 'wq_' is assigned in constructor body. Consider performing initialization in initialization list.
4. find_fuzz.cpp#L40: The function 'LLVMFuzzerTestOneInput' is never used.
5. status_fuzz.cpp#L36: Variable 'pcs_' is assigned in constructor body. Consider performing initialization in initialization list.
6. torii_fuzz.cpp#L33: Variable 'pcs_' is assigned in constructor body. Consider performing initialization in initialization list.

fixed