Fix code coverage of corelib by updating coverlet (#86566)

Author: stephentoub

.config/dotnet-tools.json

@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "coverlet.console": {
-      "version": "3.1.2",
+      "version": "6.0.0",
       "commands": [
         "coverlet"
       ]

eng/Versions.props

@@ -189,7 +189,7 @@
     <XUnitRunnerVisualStudioVersion>2.4.5</XUnitRunnerVisualStudioVersion>
     <NUnitVersion>3.12.0</NUnitVersion>
     <NUnitTestAdapterVersion>4.1.0</NUnitTestAdapterVersion>
-    <CoverletCollectorVersion>3.1.2</CoverletCollectorVersion>
+    <CoverletCollectorVersion>6.0.0</CoverletCollectorVersion>
     <NewtonsoftJsonVersion>13.0.1</NewtonsoftJsonVersion>
     <NewtonsoftJsonBsonVersion>1.0.2</NewtonsoftJsonBsonVersion>
     <SQLitePCLRawbundle_greenVersion>2.0.4</SQLitePCLRawbundle_greenVersion>