Fix #4438

There is an edge-case in FuzzyMatchV1 during backward scan, related to
normalization: if string is initially denormalized (e.g. Unicode symbol),
backward scan will proceed further to the next char; however, when the
score is computed, the string is normalized first, then scanned based on
the pattern. This leads to accessing pattern index increment, which
itself leads to out-of-bound index access, resulting in a panic.

To illustrate the process, here's the sequence of operations when search
is perfored:

1. during backward scan by "minim" pattern

```
xxxxx Minímal example
      ^^^^^^^^^^^^
      ||||||||||||
      miniiiiiiiim <- compute score for this substring
```
2. during compute score by "minim" pattern
```
      Minímal exam
      minimal exam <- normalize chars before computing the score
      ^^^^^^
      ||||||
      minim <- at this point the pattern is already fully scanned and index
              is out-of-the-bound
```

In this commit the char is normalized during backward scan, to detect
properly the boundaries for the pattern.

Go 1.24 now has a vet check about this that causes `go test` to fail:
https://github.com/golang/go/issues/60529

Close #3963

Find the last occurrence of the last character in the pattern and
perform the search algorithm only up to that point.

The effectiveness of this mechanism depends a lot on the shape of the
input and the pattern.

This gives yet another 5% boost.

This simple optmization can give more than 15% performance boost
in some scenarios.