Search default configuration load by bootstrap

[didoda]

This PR provides a default Search configuration set by BEdita/Core/config/bootstrap.php, if missing.

This is done to avoid that app that uses BEdita should explicitely set the default SimpleSearchAdapter in Search in config/app.php.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.76%. Comparing base (7af65bf) to head (50627d3). Report is 5 commits behind head on 5-salix.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 5-salix #2069 +/- ## ========================================== Coverage 98.76% 98.76% Complexity 2923 2923 ========================================== Files 229 229 Lines 10196 10196 ========================================== Hits 10070 10070 Misses 126 126 ```

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