WIP: Maintenance/cleanup webserver test fixtures

[pcrespov]

What do these changes do?

Review and cleanup of fixtures in webserver tests :

• reduce redundancy (reuse helpers from pytest-simcore)
• classify fixtures
• share common fixtures

to fulfill needs of #1724: tests for garbage collector

• a User with more then 2 projects
• a user without projects
• a user with just 1 project

The user can be:

• connected via browser (websocket connection is up)
• disconnected (no websocket connection)

Related issue number

follows from needs of #1724

How to test

Checklist

• Did you change any service's API? Then make sure to bundle document and upgrade version (make openapi-specs, git commit ... and then make version-*)
• Unit tests for the changes exist
• Runs in the swarm
• Documentation reflects the changes
• New module? Add your github username to .github/CODEOWNERS

[codecov]

Codecov Report

Merging #1731 into master will decrease coverage by 1.9%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #1731     +/-   ##
========================================
- Coverage    72.5%   70.6%   -2.0%     
========================================
  Files         279     279             
  Lines       11267   11267             
  Branches     1238    1238             
========================================
- Hits         8175    7960    -215     
- Misses       2756    2983    +227     
+ Partials      336     324     -12     

Flag	Coverage Δ
#integrationtests	56.2% <ø> (-1.0%)	⬇️
#unittests	66.4% <ø> (-0.1%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...es/sidecar/src/simcore_service_sidecar/executor.py	23.9% <0.0%> (-59.4%)	⬇️
...rvices/sidecar/src/simcore_service_sidecar/core.py	26.7% <0.0%> (-47.7%)	⬇️
services/sidecar/src/simcore_service_sidecar/db.py	52.0% <0.0%> (-40.0%)	⬇️
...vices/sidecar/src/simcore_service_sidecar/utils.py	57.7% <0.0%> (-32.4%)	⬇️
...ervices/sidecar/src/simcore_service_sidecar/cli.py	48.4% <0.0%> (-18.2%)	⬇️
.../sidecar/src/simcore_service_sidecar/log_parser.py	73.8% <0.0%> (-13.9%)	⬇️
...es/sidecar/src/simcore_service_sidecar/rabbitmq.py	88.2% <0.0%> (-1.5%)	⬇️
.../director/src/simcore_service_director/producer.py	60.1% <0.0%> (-0.3%)	⬇️

[pcrespov]

Adds in #1741