新增在线用户的搜索和一键下线功能

[lanrenwo]

RT，还可以踢除休眠的用户，避免LDAP/Radius账号被删除后，还可以重连的问题。

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 47 lines in your changes are missing coverage. Please review.

Project coverage is 18.09%. Comparing base (a59e480) to head (096b6f8).
Report is 1 commits behind head on dev.

Files	Patch %	Lines
server/sessdata/online.go	0.00%	39 Missing ⚠️
server/sessdata/session.go	0.00%	5 Missing ⚠️
server/dbdata/user_act_log.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #298      +/-   ##
==========================================
- Coverage   18.20%   18.09%   -0.12%     
==========================================
  Files          64       64              
  Lines        5339     5373      +34     
==========================================
  Hits          972      972              
- Misses       4243     4277      +34     
  Partials      124      124              

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