CMakeLists: Turn off RocksDB build extras.

[l-laura]

Turned off a bunch of CMake flags that are activated by default in RocksDB CMakeLists.

Test

Check if / how much this improves the build time.

Current main (included here): 35m 59s.
Conan-introducing branch with multi-threaded build (not included, could complement these changes): 14m 20s.

[github-actions]

Package	Line Rate	Branch Rate	Health
libs.http-datasource.src	81%	41%	✔
libs.http-service.src	80%	42%	✔
libs.logging.include.mapget	100%	0%	✔
libs.model.include.mapget.model	81%	41%	✔
libs.model.src	87%	49%	✔
libs.service.include.mapget.service	100%	0%	✔
libs.service.src	82%	45%	✔
Summary	84% (1647 / 1960)	46% (1594 / 3465)	✔

Minimum allowed line rate is 50%

[johannes-wolf]

@l-laura Please take a look at my PR #41 which improves build-time to ~15 min. The current CI build on one core only. ;)
Not ready yet, but maybe you can rebase on that branch? I will also take a look if we could create a PR on the conan-io repository for never RocksDB packages…

[l-laura]

The changes didn't seem to have much effect, so let's drop this and go with Johannes' approach :)