fix: Fix rootcoord meta mutex contention

[bigsheeper]

RootCoord meta uses copy-on-write, allowing the removal of unnecessary copies.

issue: #37630

[sre-ci-robot]

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[bigsheeper]

[mergify]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.10%. Comparing base (4df444e) to head (800d16f).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #38799   +/-   ##
=======================================
  Coverage   81.09%   81.10%           
=======================================
  Files        1383     1383           
  Lines      195636   195657   +21     
=======================================
+ Hits       158642   158678   +36     
+ Misses      31404    31384   -20     
- Partials     5590     5595    +5     

Components	Coverage Δ
Client	78.26% <ø> (ø)
Core	69.43% <ø> (ø)
Go	83.09% <100.00%> (+0.01%)	⬆️

Files with missing lines	Coverage Δ
internal/metastore/model/collection.go	83.89% <100.00%> (+2.64%)	⬆️
internal/rootcoord/meta_table.go	83.30% <100.00%> (ø)

... and 23 files with indirect coverage changes