Add --minimal/--page_limit validator options and remove old code

[ml-evs]

• Adds --minimal which skips the slow-running query tests on each endpoint.
• Adds --page_limit which can override the default page limit of 5.
• Slightly tweaks which function reports the error if single entry endpoint tests cannot be performed
• Removes the now defunct optimade.validator.data submodule.

[codecov]

Codecov Report

Merging #571 into master will increase coverage by 0.34%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master     #571      +/-   ##
==========================================
+ Coverage   91.77%   92.11%   +0.34%     
==========================================
  Files          62       61       -1     
  Lines        3220     3210      -10     
==========================================
+ Hits         2955     2957       +2     
+ Misses        265      253      -12     

Flag	Coverage Δ
project	92.11% <77.77%> (+0.34%)	⬆️
validator	64.95% <77.77%> (+0.26%)	⬆️

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

Impacted Files	Coverage Δ
optimade/validator/__init__.py	8.57% <0.00%> (-0.52%)	⬇️
optimade/validator/validator.py	82.26% <100.00%> (+0.07%)	⬆️

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[CasperWA]

Where is page_limit applied?

[ml-evs]

Where is page_limit applied?

Any time the validator hits a multi-entry endpoint, at the moment it always uses the default 5 but there doesn't seem much point in not making this configurable

[CasperWA]

Where is page_limit applied?

Any time the validator hits a multi-entry endpoint, at the moment it always uses the default 5 but there doesn't seem much point in not making this configurable

In the code, I only see the addition of the option, but never the actual use of this option.
If it's not used or fixed, then maybe we don't add it?

[CasperWA]

Cheers @ml-evs !