[Services] Update blob CMake project

Summary:
Make blob more nix friendly
and make use of the native/cpp cmake work

DatabaseEntitiesTools.h was moved to lib/src as it was largely duplicated across three projects

Backup docker + cmake is fixed in D4494

Test Plan:

nix develop
cd services/blob && mkdir build && cd build && cmake .. && make

docker:

cd services/base-image
docker build -t commapp/services-base . -f Dockerfile

cd ../..
docker build . -f services/blob/Dockerfile

Reviewers: max, karol, atul

Reviewed By: atul

Subscribers: ashoat, tomek, adrian, atul, abosh, karol, max

Differential Revision: https://phab.comm.dev/D4493