pkg/trace/traceutil: fix edge case in NormalizeTag

[ahmed-mez]

What does this PR do?

Fixes an edge case in NormalizeTag where the function can return tags longer than maxTagLength

Motivation

Bug fix

Additional Notes

Bug discovered thanks to fuzzing, the fuzz test will be introduced in #13195

--- FAIL: FuzzNormalizeTag (1.16s)
    --- FAIL: FuzzNormalizeTag (0.00s)
        fuzz_test.go:28: Max length (200) exceeded: runeCount(a00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000_00) == 201

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

Tags normalization works as expected

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[knusbaum]

Nice find.