TestToUTF8WithFallback is the cause of recurrent spurious test failures
even despite code to set the detected charset order.

The reason why this happens is because the preferred detected charset order
is not being initialised for these tests.

This PR simply ensures that this is set at the start of each test and would
allow different tests to be written to allow differing orders.

Replaces #12571
Close #12571

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Fix chardet test and add ordering option

Signed-off-by: Andrew Thornton <art27@cantab.net>

* minor fixes

Signed-off-by: Andrew Thornton <art27@cantab.net>

* remove log

Signed-off-by: Andrew Thornton <art27@cantab.net>

* remove log2

Signed-off-by: Andrew Thornton <art27@cantab.net>

* only iterate through top results

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Update docs/content/doc/advanced/config-cheat-sheet.en-us.md

* slight restructure of for loop

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

* Prevent compiler environment from making the tests fail

* Remove unused function

* Pass lint

* Make encoding tests independent of LOCALE settings

* Fix fmt

* Force CI to restart

* Convert files to utf-8 for indexing

* Move utf8 functions to modules/base

* Bump repoIndexerLatestVersion to 3

* Add tests for base/encoding.go

* Changes to pass gosimple

* Move UTF8 funcs into new modules/charset package