meta: create subdir automatically

[SandyXSD]

fix #1709

The auto-created subdir has mode 777, and uid/gid = 0.

[codecov-commenter]

Codecov Report

Merging #1712 (9037126) into main (fe910ad) will increase coverage by 0.24%.
The diff coverage is 82.85%.

@@            Coverage Diff             @@
##             main    #1712      +/-   ##
==========================================
+ Coverage   61.60%   61.85%   +0.24%     
==========================================
  Files         134      135       +1     
  Lines       22672    22876     +204     
==========================================
+ Hits        13968    14149     +181     
- Misses       7129     7136       +7     
- Partials     1575     1591      +16     

Impacted Files	Coverage Δ
pkg/meta/config.go	53.24% <0.00%> (-1.42%)	⬇️
pkg/meta/utils.go	71.18% <60.00%> (-0.49%)	⬇️
pkg/meta/dump.go	75.86% <82.97%> (+2.01%)	⬆️
pkg/meta/redis.go	73.16% <100.00%> (+0.18%)	⬆️
pkg/meta/sql.go	67.13% <100.00%> (+0.12%)	⬆️
pkg/meta/tkv.go	76.55% <100.00%> (+0.04%)	⬆️
pkg/meta/tkv_etcd.go	77.77% <0.00%> (ø)
... and 3 more

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