Add LinkBench to CoreCLR BenchView

This change adds Linker tests as scenario tests tracked in
BenchView for CoreCLR benchmarks.

The Benchmarks added are:
HelloWorld, WebAPI, CoreFx, MusicStore (MSIL and ReadyToRun), Roslyn.

The metrics are:
MSIL size before and after ILLINK
Total publish-dir size before and after ILLINK
% Reduction in MSIL and Total dir-size after linking.

Author: Swaroop Sridhar

Linked

@@ -0,0 +1,27 @@
+<linker>
+    <!--- Called by Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions:.cctor -->
+    <assembly fullname="System.Linq.Queryable">
+        <type fullname="System.Linq.Queryable" required="true" />
+    </assembly>
+
+    <assembly fullname="System.Linq.Expressions">
+        <!--- Called by System.Linq.Expressions.Expression:CreateLambda -->
+        <type fullname="System.Linq.Expressions.Expression`1" required="true" />
+        <!--- Called by [System.Linq.Expressions]System.Runtime.CompilerServices.CallSite<>.CreateCustomNoMatchDelegate and [System.Linq.Expressions]System.Runtime.CompilerServices.CallSite<>.CreateCustomUpdateDelegate-->
+        <type fullname="System.Runtime.CompilerServices.CallSiteOps" required="true" />
+        <!--- Called by [System.Linq.Expressions]System.Runtime.CompilerServices.CallSiteBinder.Stitch -->
+        <type fullname="System.Runtime.CompilerServices.CallSite" required="true" />
+        <!--- Called by [System.Linq.Expressions]System.Runtime.CompilerServices.CallSiteBinder.Stitch -->
+        <type fullname="System.Runtime.CompilerServices.CallSite`1" required="true" />
+        <!--- Called by [System.Linq.Expressions]System.Runtime.CompilerServices.CallSite`1.MakeUpdateDelegate -->
+        <type fullname="System.Dynamic.UpdateDelegates" required="true" />
+        <!--- Called by [System.Linq.Expressions]System.Dynamic.DynamicObject.MetaDynamic.BindBinaryOperation -->
+        <type fullname="System.Dynamic.DynamicObject" required="true" />
+    </assembly>
+
+    <assembly fullname="System.ComponentModel.TypeConverter">
+        <type fullname="System.ComponentModel.StringConverter" required="true" />
+        <type fullname="System.ComponentModel.BooleanConverter" required="true" />
+        <type fullname="System.ComponentModel.CollectionConverter" required="true" />
+    </assembly>
+</linker>

tests/src/performance/linkbench/assets/MusicStore/MusicStoreReflection.xml

@@ -0,0 +1,3 @@
+Microsoft.CodeAnalysis
+Microsoft.CodeAnalysis.CSharp
+System.Private.CoreLib

tests/src/performance/linkbench/assets/Roslyn/RoslynRoots.txt

@@ -0,0 +1,5 @@
+<linker>
+    <assembly fullname="csc">
+        <type fullname="*" required="true" />
+    </assembly>
+</linker>

tests/src/performance/linkbench/assets/Roslyn/RoslynRoots.xml

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <RuntimeIdentifiers>win7-x86;win7-x64</RuntimeIdentifiers>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="ILLink.Tasks" Version="0.1.0-preview" />
+  </ItemGroup>
+</Project>