Fix sanitizeEntity's includeFields usage

[Convly]

Fix #7335

In sanitizeEntity, setting includeFields to null should indicates "all fields".
It was not the case before thus creating issues with allowedFieldsHasKey checks for dynamic zones.

[codecov]

Codecov Report

Merging #7350 into master will increase coverage by 0.05%.
The diff coverage is 51.28%.

@@            Coverage Diff             @@
##           master    #7350      +/-   ##
==========================================
+ Coverage   26.17%   26.22%   +0.05%     
==========================================
  Files        1130     1131       +1     
  Lines       15415    15433      +18     
  Branches     2439     2443       +4     
==========================================
+ Hits         4035     4048      +13     
- Misses       9561     9565       +4     
- Partials     1819     1820       +1     

Flag	Coverage Δ
#front	18.26% <0.00%> (-0.01%)	⬇️
#unit	53.14% <100.00%> (+0.17%)	⬆️

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

Impacted Files	Coverage Δ
...s/strapi-admin/admin/src/containers/Admin/index.js	63.82% <ø> (ø)
...admin/admin/src/containers/Roles/EditPage/index.js	2.77% <0.00%> (-0.80%)	⬇️
...admin/admin/src/containers/Roles/ListPage/index.js	0.00% <0.00%> (ø)
...ermissions/admin/src/components/PopUpForm/index.js	0.00% <0.00%> (ø)
packages/strapi-admin/services/metrics.js	100.00% <100.00%> (ø)
packages/strapi-admin/services/role.js	94.11% <100.00%> (+0.14%)	⬆️
packages/strapi-admin/services/user.js	82.56% <100.00%> (+0.66%)	⬆️
packages/strapi-utils/lib/sanitize-entity.js	61.29% <100.00%> (ø)
packages/strapi/lib/services/metrics/sender.js	100.00% <100.00%> (ø)

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[alexandrebodin]

LGTM