Replace delegate with function in LazyString

[andrey-zherikov]

Closes #113

[codecov[bot]]

Codecov Report

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

Comparison is base (e206434) 99.10% compared to head (eb37bdd) 99.10%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #160 +/- ## ========================================== - Coverage 99.10% 99.10% -0.01% ========================================== Files 28 28 Lines 2016 2015 -1 ========================================== - Hits 1998 1997 -1 Misses 18 18 ```

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