enhance: scann support search parameter 'ensure_topk_full'

[cqy123456]

issue: #909
related pr：#353

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[mergify]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.07%. Comparing base (3c46f4c) to head (0008c75).
Report is 314 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##           main    #1072       +/-   ##
=========================================
+ Coverage      0   72.07%   +72.07%     
=========================================
  Files         0       86       +86     
  Lines         0     8204     +8204     
=========================================
+ Hits          0     5913     +5913     
- Misses        0     2291     +2291     

see 86 files with indirect coverage changes

[alexanderguzhva]

/lgtm
overall

[foxspy]

/kind improvement