chore(rls): move to feature flag and disable related view

[villebro]

SUMMARY

Minor refinements to Row Level Security (RLS) implementation:

• Move ENABLE_ROW_LEVEL_SECURITY from config flag to feature flag.
• Remove RLS from table view related view. Currently non-admin users can see all RLS filters that apply to a table, which can be both a security concern and a privacy issue.
• Disable Row Level Security and Row Level Security Filters view menus for other users than Admin.

TEST PLAN

Local testing

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[codecov-io]

Codecov Report

Merging #11575 into master will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #11575      +/-   ##
==========================================
- Coverage   59.59%   59.57%   -0.03%     
==========================================
  Files         832      832              
  Lines       40482    40481       -1     
  Branches     3666     3666              
==========================================
- Hits        24126    24117       -9     
- Misses      16187    16195       +8     
  Partials      169      169              

Flag	Coverage Δ
cypress	55.01% <ø> (+<0.01%)	⬆️
python	62.06% <100.00%> (-0.04%)	⬇️

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

Impacted Files	Coverage Δ
superset/config.py	90.11% <ø> (-0.04%)	⬇️
superset/connectors/sqla/views.py	67.26% <ø> (ø)
superset/security/manager.py	90.90% <ø> (ø)
superset/app.py	81.29% <100.00%> (ø)
superset/common/query_context.py	87.87% <100.00%> (ø)
superset/connectors/sqla/models.py	90.36% <100.00%> (-0.27%)	⬇️
superset/viz.py	57.74% <100.00%> (ø)
superset/db_engine_specs/sqlite.py	65.62% <0.00%> (-9.38%)	⬇️
superset/utils/celery.py	82.14% <0.00%> (-3.58%)	⬇️
superset/result_set.py	96.69% <0.00%> (-1.66%)	⬇️
... and 3 more

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