[security] Moving set/merge perm to security manager

[john-bodley]

This PR refactors (copy and paste) the helper set_perm and merge_perm methods to be encompassed within the security manager which ensures that the manager controls all reads/writes related to data permissions.

Note the helpers.merge_perm logic is part of SupersetSecurityManager.set_perm as there already exists a SupersetSecurityManager.merge_perm method. Though the logic is similar the database connection logic differs. When I tried to use the later, though I was able to read, writes failed with the following exception,

sqlalchemy.exc.ResourceClosedError: This transaction is closed

hence the reason for simply copy-and-pasting the current logic. The one exception is the permission and view_menu should only be refreshed only if updated.

Finally I'm also perplexed as to why the pylint warnings are present (which I've ignored).

to: @jeffreythewang @mistercrunch @timifasubaa

[mistercrunch]

LGTM

[mistercrunch]

Hey I think we can get rid of most of this by calling self.add_permission_view_menu which takes care of all of this I think

[john-bodley]

@mistercrunch I tried that approach earlier (see description) which lead to the following exception being thrown: sqlalchemy.exc.ResourceClosedError: This transaction is closed

[mistercrunch]

Yeah the context is funky here where we're inside some sort of SQLAlchemy trigger. Feel free to merge as is.

[codecov-io]

Codecov Report

Merging #5684 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #5684      +/-   ##
==========================================
- Coverage    63.5%   63.49%   -0.01%     
==========================================
  Files         360      360              
  Lines       22922    22920       -2     
  Branches     2555     2555              
==========================================
- Hits        14556    14554       -2     
  Misses       8351     8351              
  Partials       15       15

Impacted Files	Coverage Δ
superset/models/helpers.py	85.97% <ø> (-1.73%)	⬇️
superset/connectors/druid/models.py	82.56% <100%> (ø)	⬆️
superset/models/core.py	85.09% <100%> (ø)	⬆️
superset/security.py	75.55% <100%> (+2.64%)	⬆️
superset/connectors/sqla/models.py	78.62% <100%> (-0.05%)	⬇️

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