Implement TrimmingDescriptorNode for ILTrim XML descriptor support

[Copilot]

Description

The -x (XML descriptor) command-line option was unimplemented for ILTrim — the #if !ILTRIM block in Driver.cs simply skipped descriptor processing. This reuses TrimmingDescriptorNode from ILCompiler.Compiler to implement it.

Changes

• Driver.cs (illink): Added TrimmingDescriptorNode using alias under #if ILTRIM; replaced the no-op #if !ILTRIM with inputs.Add(new TrimmingDescriptorNode(xmlFile))
• TrimmingDescriptorNode.cs: Added #if ILTRIM to use factory.Logger/factory.Settings.FeatureSettings instead of MetadataManager; guarded ICompilationRootProvider with #if !ILTRIM (not available in ILTrim)
• ILTrim.Core.csproj: Included TrimmingDescriptorNode.cs as a linked compile item
• ILTrimExpectedFailures.txt: Removed 23 now-passing tests (mostly LinkXml.* and some Inheritance.Interfaces.*); added 1 new expected failure (LinkXml.UnusedNonRequiredTypeIsRemoved — inherits NativeAOT's DescriptorMarker semantics which don't honor required="0")

Test results: 0 failures, 308 passed (up from 285), 604 skipped.

[Copilot]

Pull request overview

Implements support for ILTrim’s -x (XML descriptor) option by reusing the NativeAOT TrimmingDescriptorNode, enabling descriptor-based rooting during ILTrim runs and updating ILTrim test expectations accordingly.

Changes:

• Enabled -x processing under ILTRIM by adding TrimmingDescriptorNode to ILTrim inputs instead of skipping descriptor handling.
• Updated TrimmingDescriptorNode to compile and function under ILTRIM by using ILTrim’s NodeFactory logging/settings surface and excluding ICompilationRootProvider where unavailable.
• Updated ILTrim expected failures list to reflect newly passing descriptor-related tests and added one expected failure due to semantic differences.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/tools/illink/src/linker/Linker/Driver.cs	Wires -x into ILTrim by adding TrimmingDescriptorNode to ILTrim inputs.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/TrimmingDescriptorNode.cs	Adds #if ILTRIM adaptations for logger/settings and guards ICompilationRootProvider.
src/coreclr/tools/ILTrim.Core/ILTrim.Core.csproj	Links TrimmingDescriptorNode.cs into ILTrim.Core so ILTrim can use it.
src/coreclr/tools/ILTrim.Tests/ILTrimExpectedFailures.txt	Removes now-passing tests from expected failures; adds one new expected failure.

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