Feat: Add dashboard milestone search and repo milestone search by name.

[rogerluo410]

Feature for issue 13845:

• Add milestones search by name on dashboard milestones page.
• Add milestones search by name on repo issue/milestones page.

Two features merged to one PR.

Origin PR:
#14806

Issue link:
#13845

close #13845

[zeripath]

you need to run go fmt on these files too.

[codecov-io]

Codecov Report

Merging #14866 (0c29954) into master (487f2ee) will decrease coverage by 0.09%.
The diff coverage is 41.60%.

@@            Coverage Diff             @@
##           master   #14866      +/-   ##
==========================================
- Coverage   42.21%   42.11%   -0.10%     
==========================================
  Files         767      774       +7     
  Lines       81624    83045    +1421     
==========================================
+ Hits        34458    34977     +519     
- Misses      41531    42385     +854     
- Partials     5635     5683      +48     

Impacted Files	Coverage Δ
cmd/dump.go	0.93% <0.00%> (-0.01%)	⬇️
cmd/serv.go	2.61% <0.00%> (-0.02%)	⬇️
cmd/web.go	0.00% <0.00%> (ø)
cmd/web_graceful.go	0.00% <0.00%> (ø)
cmd/web_letsencrypt.go	0.00% <0.00%> (ø)
models/action.go	48.52% <0.00%> (-2.42%)	⬇️
models/migrations/migrations.go	2.59% <ø> (ø)
models/migrations/v130.go	0.00% <0.00%> (ø)
models/migrations/v166.go	0.00% <0.00%> (ø)
models/migrations/v172.go	0.00% <0.00%> (ø)
... and 190 more

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[6543]

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