refactor(cli): Adopt PolySharp to manage polyfills and remove custom implementations

Author: arturcic

new-cli/Directory.Packages.props

@@ -22,6 +22,7 @@
     </PackageVersion>
     <PackageVersion Include="NUnit3TestAdapter" Version="6.2.0" />
     <PackageVersion Include="Polly" Version="8.6.6" />
+    <PackageVersion Include="PolySharp" Version="1.15.0" />
     <PackageVersion Include="Roslynator.Analyzers" Version="4.15.0" />
     <PackageVersion Include="Roslynator.Formatting.Analyzers" Version="4.15.0" />
     <!-- specific packages -->

new-cli/GitVersion.Cli.Generator/GitVersion.Cli.Generator.csproj

@@ -6,12 +6,17 @@
         <PackageScribanIncludeSource>true</PackageScribanIncludeSource>
         <SatelliteResourceLanguages>en</SatelliteResourceLanguages>
         <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
+        <NoWarn>$(NoWarn);CS8669</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>
         <PackageReference Include="Microsoft.CSharp" />
         <PackageReference Include="Microsoft.CodeAnalysis.CSharp" PrivateAssets="all" />
         <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" PrivateAssets="all" />
+        <PackageReference Include="PolySharp">
+          <PrivateAssets>all</PrivateAssets>
+          <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+        </PackageReference>
         <PackageReference Include="Scriban" IncludeAssets="Build" />
         <PackageReference Include="System.Text.Json" />
     </ItemGroup>