FormattedLogValues - Small optimization for index operator

[snakefoot]

Resolves #122046 (Removed "expensive" Count-check, since also exists in LogValuesFormatter)

Method	Mean	Error	StdDev	Gen0	Allocated
FormattedLogValues_Lookup (Before)	5.429 ns	0.0971 ns	0.0908 ns	-	-
FormattedLogValues_Lookup (After)	4.295 ns	0.0159 ns	0.0149 ns	-	-

Benchmark code:

    public class FormattedLogValuesTest
    {
        FormattedLogValues _test = new FormattedLogValues("{0} {1} {2}", new object[] { "Hello", "Cruel", "World" });

        [Benchmark]
        public void FormattedLogValues_Lookup()
        {
            var parameterCount = _test.Count;
            for (int i = 0; i < parameterCount; ++i)
            {
                var parameter = _test[i];
                if (parameter.Key is null)
                    return;
            }
        }
    }

[Copilot]

Pull request overview

This PR optimizes the indexer operator in FormattedLogValues by removing a redundant check for the last element (original format). Previously, the indexer explicitly checked if index == Count - 1 to return the original format, but this check was redundant since LogValuesFormatter.GetValue() already handles this case. The optimization reduces execution time by ~20% (from 5.4ns to 4.3ns) by delegating all logic to GetValue when a formatter exists, eliminating the duplicate check.

Key changes:

• Restructured indexer logic to check for null formatter/values upfront and delegate to GetValue otherwise
• Removed redundant index == Count - 1 check since GetValue handles the last index internally

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[tarekgh]

LGTM, thanks @snakefoot!