FileConfigurationProvider.Dispose should dispose FileProvider when it owns it

[adamsitnik]

The app that I've used for leak detection and confirmation of the fix:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Configuration" Version="7.0.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.Xml" Version="7.0.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="settings.xml">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
  </ItemGroup>
</Project>

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
	<MySettings>
		<SomeSetting>Test</SomeSetting>
		<Another>true</Another>
	</MySettings>
</configuration>

using Microsoft.Extensions.Configuration;

namespace ConfigLeak
{
    internal class Program
    {
        static void Main()
        {
            const int iterations = 2;

            Console.WriteLine("Press a key");
            Console.ReadKey();

            for (var i = 0; i < iterations; i++)
            {
                Test();

                Console.WriteLine("Take a snapshot and press a key");
                Console.ReadKey();
            }
        }

        static void Test()
        {
            var config = new ConfigurationBuilder().AddXmlFile("settings.xml", false, true).Build();

            (config as IDisposable)?.Dispose();
        }
    }
}

Before:

After:

The only tricky thing is that the FileProvider can be also provided by the user, so we can not just always dispose it.

fixes #86146

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Issue Details

---

The app that I've used for leak detection and confirmation of the fix:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Configuration" Version="7.0.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.Xml" Version="7.0.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="settings.xml">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
  </ItemGroup>
</Project>

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
	<MySettings>
		<SomeSetting>Test</SomeSetting>
		<Another>true</Another>
	</MySettings>
</configuration>

using Microsoft.Extensions.Configuration;

namespace ConfigLeak
{
    internal class Program
    {
        static void Main()
        {
            const int iterations = 2;

            Console.WriteLine("Press a key");
            Console.ReadKey();

            for (var i = 0; i < iterations; i++)
            {
                Test();

                Console.WriteLine("Take a snapshot and press a key");
                Console.ReadKey();
            }
        }

        static void Test()
        {
            var config = new ConfigurationBuilder().AddXmlFile("settings.xml", false, true).Build();

            (config as IDisposable)?.Dispose();
        }
    }
}

Before:

After:

The only tricky thing is that the FileProvider can be also provided by the user, so we can not just always dispose it.

fixes #86146

Author:	adamsitnik
Assignees:	-
Labels:	area-Extensions-Configuration
Milestone:	8.0.0