[Refactor] Unexport newRepoRedirect() & rm dedub del exec

[6543]

while looking at #11649 I noticed things i fixed & refactored are copy-pasted things from ReopRedirect

[codecov-io]

Codecov Report

Merging #14441 (75ddcc3) into master (525d75c) will increase coverage by 0.00%.
The diff coverage is 33.33%.

@@           Coverage Diff           @@
##           master   #14441   +/-   ##
=======================================
  Coverage   41.76%   41.77%           
=======================================
  Files         748      748           
  Lines       80103    80101    -2     
=======================================
+ Hits        33455    33462    +7     
+ Misses      41125    41119    -6     
+ Partials     5523     5520    -3     

Impacted Files	Coverage Δ
models/repo.go	52.41% <0.00%> (+0.08%)	⬆️
models/repo_redirect.go	70.83% <66.66%> (ø)
models/gpg_key.go	53.33% <0.00%> (-0.58%)	⬇️
services/pull/pull.go	42.15% <0.00%> (-0.50%)	⬇️
modules/git/batch_reader_nogogit.go	46.26% <0.00%> (+1.49%)	⬆️
modules/charset/charset.go	73.03% <0.00%> (+4.49%)	⬆️
modules/git/repo_language_stats_nogogit.go	63.82% <0.00%> (+6.38%)	⬆️
modules/indexer/stats/db.go	68.00% <0.00%> (+12.00%)	⬆️

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[zeripath]

Just roll this into to #11649 - saves the CI and approval time.

[6543]

included in #11649