Rename SourceBuildUseMonoRuntime property, which is not SB specific

This is a coordinated cross-repo change, and might break the build until
all four PRs are merged. The other three are:

Ref: dotnet/source-build#4165

Directory.Build.props

@@ -39,7 +39,7 @@
     <!-- Set PublishReadyToRun to speed up the build. -->
     <EnablePublishReadyToRun>true</EnablePublishReadyToRun>
     <!-- Crossgen2 is not built with source-built Mono-based .NET SDKs. -->
-    <EnablePublishReadyToRun Condition="'$(SourceBuildUseMonoRuntime)' == 'true'">false</EnablePublishReadyToRun>
+    <EnablePublishReadyToRun Condition="'$(DotNetBuildUseMonoRuntime)' == 'true'">false</EnablePublishReadyToRun>
   </PropertyGroup>
 
   <Import Project="$(RepoRoot)/Directory.Build.props.user" Condition="Exists('$(RepoRoot)/Directory.Build.props.user')" />

eng/DotNetBuild.props

@@ -30,7 +30,7 @@
 
     <PropertyGroup>
       <SourceBuildBootstrapTfmArg Condition="$(SourceBuildBootstrapTfm) != ''">--tfm $(SourceBuildBootstrapTfm)</SourceBuildBootstrapTfmArg>
-      <SourceBuildUseMonoRuntime Condition="'$(SourceBuildUseMonoRuntime)' == ''">false</SourceBuildUseMonoRuntime>
+      <DotNetBuildUseMonoRuntime Condition="'$(DotNetBuildUseMonoRuntime)' == ''">false</DotNetBuildUseMonoRuntime>
     </PropertyGroup>
 
     <!-- this runs the source-build bootstrap path as described in https://github.com/dotnet/fsharp/blob/95df49e380ea8dbf33653fa4209f89dba29413f5/eng/build.sh#L247
@@ -41,7 +41,7 @@
          -bl enables the binlogs for the tools and Proto builds, which make debugging failures here easier
     -->
     <Exec
-      Command="./build.sh --bootstrap --skipBuild -bl $(SourceBuildBootstrapTfmArg) /p:SourceBuildUseMonoRuntime=$(SourceBuildUseMonoRuntime) /p:DotNetBuildSourceOnly=true /p:DotNetBuildInnerRepo=true /p:DotNetBuildRepo=true /p:DotNetBuildOrchestrator=$(DotNetBuildOrchestrator)"
+      Command="./build.sh --bootstrap --skipBuild -bl $(SourceBuildBootstrapTfmArg) /p:DotNetBuildUseMonoRuntime=$(DotNetBuildUseMonoRuntime) /p:DotNetBuildSourceOnly=true /p:DotNetBuildInnerRepo=true /p:DotNetBuildRepo=true /p:DotNetBuildOrchestrator=$(DotNetBuildOrchestrator)"
       WorkingDirectory="$(InnerSourceBuildRepoRoot)"
       EnvironmentVariables="@(InnerBuildEnv)" />
   </Target>