meta: limit the number of clients running background cleanup jobs

[SandyXSD]

close #1358

[codecov-commenter]

Codecov Report

Merging #1393 (fdce1a1) into main (1bc8a6a) will decrease coverage by 0.05%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##             main    #1393      +/-   ##
==========================================
- Coverage   59.54%   59.49%   -0.06%     
==========================================
  Files         128      128              
  Lines       21723    21722       -1     
==========================================
- Hits        12935    12923      -12     
- Misses       7251     7255       +4     
- Partials     1537     1544       +7     

Impacted Files	Coverage Δ
pkg/meta/base.go	73.31% <44.44%> (+1.68%)	⬆️
pkg/meta/sql.go	67.42% <100.00%> (-0.30%)	⬇️
pkg/meta/tkv.go	75.27% <0.00%> (-0.77%)	⬇️
pkg/chunk/cached_store.go	73.18% <0.00%> (-0.35%)	⬇️
pkg/meta/redis.go	70.94% <0.00%> (-0.05%)	⬇️
pkg/vfs/handle.go	86.44% <0.00%> (+0.84%)	⬆️

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