vfs: write control file asynchronously

[SandyXSD]

fix #1739

Reference: https://code.google.com/archive/p/macfuse/wikis/OPTIONS.wiki

[codecov-commenter]

Codecov Report

Merging #1747 (b7789b3) into main (2c88893) will increase coverage by 0.18%.
The diff coverage is 45.45%.

@@            Coverage Diff             @@
##             main    #1747      +/-   ##
==========================================
+ Coverage   61.68%   61.87%   +0.18%     
==========================================
  Files         135      135              
  Lines       22908    22935      +27     
==========================================
+ Hits        14131    14190      +59     
+ Misses       7181     7153      -28     
+ Partials     1596     1592       -4     

Impacted Files	Coverage Δ
cmd/format.go	60.89% <0.00%> (-1.61%)	⬇️
pkg/object/encrypt.go	68.29% <45.45%> (ø)
cmd/warmup.go	64.66% <50.00%> (+0.43%)	⬆️
cmd/rmr.go	62.29% <60.00%> (+1.27%)	⬆️
cmd/info.go	69.51% <66.66%> (+1.15%)	⬆️
pkg/vfs/vfs.go	77.98% <100.00%> (+0.06%)	⬆️
pkg/meta/sql.go	67.13% <0.00%> (-0.11%)	⬇️
pkg/object/b2.go	2.12% <0.00%> (-0.05%)	⬇️
pkg/meta/base.go	71.69% <0.00%> (+0.50%)	⬆️
... and 3 more

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