Add DebuggerDisableUserUnhandledExceptionsAttribute

[halter73]

• Also add Debugger.BreakForUserUnhandledException(Exception)

Fixes #103105

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[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

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[stephentoub]

Thanks.

[eerhardt]

It probably isn't going to make much of a difference, but should we add this new attribute to

runtime/src/libraries/System.Private.CoreLib/src/ILLink/ILLink.LinkAttributes.Shared.xml

Lines 2 to 31 in d710379

	<!-- The following attributes are only necessary when debugging is supported -->
	<assembly fullname="System.Private.CoreLib" feature="System.Diagnostics.Debugger.IsSupported" featurevalue="false">
	<type fullname="System.Diagnostics.DebuggableAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	<type fullname="System.Diagnostics.DebuggerBrowsableAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	<type fullname="System.Diagnostics.DebuggerDisplayAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	<type fullname="System.Diagnostics.DebuggerHiddenAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	<type fullname="System.Diagnostics.DebuggerNonUserCodeAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	<type fullname="System.Diagnostics.DebuggerStepperBoundaryAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	<type fullname="System.Diagnostics.DebuggerStepThroughAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	<type fullname="System.Diagnostics.DebuggerTypeProxyAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	<type fullname="System.Diagnostics.DebuggerVisualizerAttribute">
	<attribute internal="RemoveAttributeInstances" />
	</type>
	</assembly>

That way it gets trimmed when DebuggerSupport is off.