meta/tikv: add background GC worker for TiKV

[SandyXSD]

The GC cleans up old entries before 3 hours by default, and can be configured with the query string "gc-interval".
It should be disabled by setting "gc-interval=0" if there's already TiDB daemon or any other service that can trigger the GC deployed.

Refs: https://github.com/tikv/client-go/blob/master/examples/gcworker/gcworker.go

[codecov-commenter]

Codecov Report

Base: 55.51% // Head: 55.37% // Decreases project coverage by -0.15% ⚠️

Coverage data is based on head (b8d4db5) compared to base (944ab73).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3262      +/-   ##
==========================================
- Coverage   55.51%   55.37%   -0.15%     
==========================================
  Files         142      142              
  Lines       33339    33362      +23     
==========================================
- Hits        18508    18473      -35     
- Misses      12885    12941      +56     
- Partials     1946     1948       +2     

Impacted Files	Coverage Δ
pkg/meta/tkv.go	70.79% <0.00%> (-0.62%)	⬇️
pkg/meta/tkv_badger.go	73.38% <0.00%> (-0.54%)	⬇️
pkg/meta/tkv_etcd.go	77.58% <0.00%> (-0.34%)	⬇️
pkg/meta/tkv_fdb.go	79.41% <0.00%> (-0.79%)	⬇️
pkg/meta/tkv_mem.go	91.90% <0.00%> (-0.54%)	⬇️
pkg/meta/tkv_tikv.go	62.75% <0.00%> (-3.19%)	⬇️
pkg/vfs/reader.go	79.27% <0.00%> (-2.38%)	⬇️
pkg/fs/fs.go	73.29% <0.00%> (-1.65%)	⬇️
pkg/vfs/handle.go	83.58% <0.00%> (-0.75%)	⬇️
pkg/chunk/disk_cache.go	73.98% <0.00%> (-0.44%)	⬇️
... and 4 more

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