[Fixes #11977] B/R should only deal with data

[etj]

According to #11977, removed the backup and restoring of

• templates
• static dirs
• static root

Also taking care of

• #12002
• #12003

Checklist

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[codecov[bot]]

Codecov Report

Merging #12007 (0435355) into master (023761d) will decrease coverage by 0.12%. The diff coverage is 11.11%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #12007      +/-   ##
==========================================
- Coverage   63.67%   63.56%   -0.12%     
==========================================
  Files         867      867              
  Lines       52664    52529     -135     
  Branches     6600     6568      -32     
==========================================
- Hits        33535    33388     -147     
- Misses      17610    17630      +20     
+ Partials     1519     1511       -8