optimize the first and last operator for a frozen-sequence and optimize the frozen-sequence value-enumerator

[fembina]

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[Copilot]

Pull Request Overview

This PR optimizes the enumeration logic and operator implementations for frozen sequences with targeted performance improvements. Key changes include:

• Adjustments in ValueEnumerator to initialize the enumerator index at –1 and update MoveNext/Reset logic.
• Replacing foreach iterations with for loops using MemoryMarshal.GetArrayDataReference in the First and Last operator implementations.
• Updates to benchmark setup to focus on the performance of the Last operator.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Sources/Falko.Common.Sequences/Sequences/FrozenSequence.ValueEnumerator.cs	Optimized enumerator logic for improved iteration handling.
Sources/Falko.Common.Sequences/Sequences/FrozenSequence.Operator.Last.cs	Revised Last/LastOrDefault implementations with inlined array accesses; removed explicit empty sequence checks.
Sources/Falko.Common.Sequences/Sequences/FrozenSequence.Operator.First.cs	Updated First operator to use for loops for performance gains.
Sources/Falko.Common.Sequences/Asserts/SequenceExceptions.cs	Removed aggressive inlining on the Not-Match exception throw.
Benchmarks/Benchmarks/Program.cs	Benchmark configuration updated to run LastOperatorBenchmark only.
Benchmarks/Benchmarks/LastOperatorBenchmark.cs and FirstOperatorBenchmark.cs	Benchmark classes setup to measure operator performance improvements.

Comments suppressed due to low confidence (2)

Benchmarks/Benchmarks/Program.cs:5

• Only the LastOperatorBenchmark is executed in the updated Program.cs, which omits performance testing for the First operator. Consider including benchmarks for the First operator as well to ensure comprehensive performance evaluation.

BenchmarkRunner.Run<LastOperatorBenchmark>();

Sources/Falko.Common.Sequences/Sequences/FrozenSequence.Operator.Last.cs:24

• The removal of the empty sequence check (SequenceExceptions.ThrowIfEmpty) in the Last method might lead to unexpected behavior when the sequence is empty. Please verify that this behavioral change is intentional, or reinstate the check to maintain consistent exception throwing.

var itemsCount = _itemsCount;