chore(dao): Organize DAOs according to SIP-92

[john-bodley]

SUMMARY

This PR is the first of many to related to SIP-92 Proposal for restructuring the Python code base. Specifically it organizes all the DAOs under the superset/daos subfolder. A few things of note:

1. The EmbeddedDAO was renamed EmbeddedDashboardDAO for clarity.
2. The organization is flat from a directory standpoint (akin to @ktmud's suggestion in the SIP) as opposed to tiered. This means that there was consolidation of DAOs by theme:

• AnnotationLayerDAO is housed in daos/annotation.py
• EmbeddedDashboardDAO and FilterSetDAO are housed in daos/dashboard.py
• SavedQueryDAO is housed in daos/query.py
• SSHTunnelDAO is housed in daos/database.py

3. It wasn't overly clear whether the modules should use singular or plural forms, i.e., dashboard or dashboards. I opted for the former given that:

• They're already housed under daos (plural) subfolder.
• Even though the dashboard.py file contains a collection of DAOs (DashboardDAO, EmbeddedDashboardDAO) we tend to think of the term "dashboard" as a concept/type rather than multiple types.
• It seems prudent to stick with either singular or plural from a consistency standpoint—the one exception is (no pun intended) exceptions as this houses different exception types and is consistent with how other files containing exceptions are named.

4. Apart from singularizing the terms the follow renames occurred:

• css_templates/dao.py became daos/css.py
• row_level_security/dao.py became daos/security.py

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

CI.

ADDITIONAL INFORMATION

• Has associated issue: [SIP-92] Proposal for restructuring the Python code base #20630
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #24331 (a16096e) into master (38ff5d3) will decrease coverage by 0.02%.
The diff coverage is 95.11%.

❗ Current head a16096e differs from pull request most recent head aafa73c. Consider uploading reports for the commit aafa73c to get more accurate results

@@            Coverage Diff             @@
##           master   #24331      +/-   ##
==========================================
- Coverage   68.93%   68.91%   -0.02%     
==========================================
  Files        1904     1899       -5     
  Lines       73878    73842      -36     
  Branches     8119     8119              
==========================================
- Hits        50927    50891      -36     
  Misses      20840    20840              
  Partials     2111     2111              

Flag	Coverage Δ
hive	53.90% <79.69%> (-0.05%)	⬇️
mysql	79.23% <94.73%> (-0.03%)	⬇️
postgres	79.32% <94.73%> (-0.03%)	⬇️
presto	53.81% <79.69%> (-0.05%)	⬇️
python	83.31% <95.11%> (-0.02%)	⬇️
sqlite	77.81% <93.60%> (-0.03%)	⬇️
unit	54.60% <79.69%> (-0.05%)	⬇️

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

Impacted Files	Coverage Δ
superset-frontend/src/pages/DatabaseList/index.tsx	65.13% <ø> (-0.32%)	⬇️
superset/commands/importers/v1/examples.py	0.00% <0.00%> (ø)
superset/common/query_object_factory.py	91.89% <0.00%> (ø)
superset/daos/exceptions.py	100.00% <ø> (ø)
superset/sqllab/sql_json_executer.py	74.39% <0.00%> (ø)
superset/sqllab/commands/execute.py	89.07% <33.33%> (ø)
superset/daos/query.py	95.23% <83.33%> (ø)
superset/daos/annotation.py	87.75% <85.00%> (ø)
superset/daos/dashboard.py	96.74% <94.59%> (ø)
...otation_layers/annotations/commands/bulk_delete.py	87.50% <100.00%> (ø)
... and 106 more

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[dpgaspar]

This is great!

"one exception is exceptions" :)