Fix IsEquivalentTo documentation - remove non-existent IgnoringOrder method

[Copilot]

Documentation incorrectly referenced a .IgnoringOrder() method that doesn't exist. Issue also asked whether global configuration for CollectionOrdering default behavior would be useful.

Changes

Documentation fixes (collections.md):

• Removed non-existent .IgnoringOrder() method reference
• Clarified that order is ignored by default - no method call needed
• Added explicit CollectionOrdering.Matching examples for order-sensitive comparisons
• Added "Practical Tips for Collection Ordering" section covering common scenarios

Documentation consistency (troubleshooting.md):

• Updated to show CollectionOrdering.Matching as the correct approach for ordered comparisons

Behavior (unchanged)

// Default: order ignored
await Assert.That(new[] { 1, 2, 3 }).IsEquivalentTo(new[] { 3, 2, 1 });  // ✅ Passes

// Explicit: order must match
await Assert.That(new[] { 1, 2, 3 })
    .IsEquivalentTo(new[] { 1, 2, 3 }, CollectionOrdering.Matching);  // ✅ Passes

await Assert.That(new[] { 1, 2, 3 })
    .IsEquivalentTo(new[] { 3, 2, 1 }, CollectionOrdering.Matching);  // ❌ Fails

Decision: No global configuration

Explicit CollectionOrdering parameter maintains clarity and follows industry patterns (NUnit, xUnit, MSTest). Default behavior (order-agnostic) is correct for most use cases.

Original prompt

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This section details on the original issue you should resolve

<issue_title>IsEquivalentTo default behavior + docs</issue_title>
<issue_description>Regarding the docs for IsEquivalentTo()

IgnoringOrder() does not seem to exist (which makes sense given that order is ignored by default).

Might it be useful if the default behaviour could be configured globally, rather than having to supply the CollectionOrdering parameter each time?</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes IsEquivalentTo default behavior + docs #3717

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