Various reliability fixes (mostly in tests)

[bart-vmware]

Description

This PR fixes leaked resources, such as proper disposal of configuration providers with file system watchers attached, as well as disposing objects related to HttpClient usage. It affects tests for the most part, but also includes a few Steeltoe fixes. Another notable pattern in tests is where a host builder is created, but never built or started, resulting in their resources in IConfiguration never getting disposed.

Before review, start by reading the new pattern in ConfigurationBuilderExtensions (in the TestResources project):

/// There are basically two patterns to ensure configuration providers are properly disposed in tests.
/// <para>
/// <example>
/// 1. Simple tests without a service provider in a using statement:<![CDATA[
/// using var root = new ConfigurationBuilder().Add(...).BuildAsRoot();
/// ]]>
/// </example>
/// </para>
/// <para>
/// <example>
/// 2. Tests where the service provider disposes the configuration by passing a lambda:
/// <![CDATA[
/// var root = new ConfigurationBuilder().Add(...).Build();
/// 
/// var services = new ServiceCollection();
/// services.AddSingleton<IConfiguration>(_ => root);
/// ]]>
/// </example>
/// </para>
public static ConfigurationRoot BuildAsRoot(this IConfigurationBuilder builder)
{
    return (ConfigurationRoot)builder.Build();
}

Why?

• IConfigurationRoot is not disposable, which is why the BuildAsRoot extension method is being introduced: it allows to track all usages and the callers don't need to cast to ConfigurationRoot (which is disposable).

• Taking a lambda in AddSingleton ensures ownership is taken, which is not the case when passing an instance directly.

Additionally, see the commit messages for details.

Quality checklist

• Your code complies with our Coding Style.
• You've updated unit and/or integration tests for your change, where applicable.
• You've updated documentation for your change, where applicable.
  If your change affects other repositories, such as Documentation and/or Samples, add linked PRs here.
• There's an open issue for the PR that you are making. If you'd like to propose a new feature or change, please open an issue to discuss the change or find an existing issue.
• You've added required license files and/or file headers (explaining where the code came from with proper attribution), where code is copied from StackOverflow, a blog, or OSS.

[github-actions]

Summary - All Code Coverage (ubuntu-latest)

Assembly	Line coverage	Branch coverage
Steeltoe.Bootstrap.AutoConfiguration	97.4%	83.3%
Steeltoe.Common	92.9%	84.4%
Steeltoe.Common.Certificates	95.6%	83.3%
Steeltoe.Common.Hosting	83.5%	65%
Steeltoe.Common.Http	97.2%	80.9%
Steeltoe.Common.Logging	82.9%	56.2%
Steeltoe.Common.Net	64.5%	66.6%
Steeltoe.Configuration.Abstractions	96.3%	89.4%
Steeltoe.Configuration.CloudFoundry	98.4%	92.7%
Steeltoe.Configuration.ConfigServer	92.1%	87.2%
Steeltoe.Configuration.Encryption	97.6%	87.5%
Steeltoe.Configuration.Kubernetes.ServiceBindings	95.6%	82.1%
Steeltoe.Configuration.Placeholder	94%	82.6%
Steeltoe.Configuration.RandomValue	93.2%	83.3%
Steeltoe.Configuration.SpringBoot	98.3%	85%
Steeltoe.Connectors	94.5%	85.5%
Steeltoe.Connectors.EntityFrameworkCore	81%	70.8%
Steeltoe.Discovery.Configuration	96.3%	75%
Steeltoe.Discovery.Consul	91.5%	84.5%
Steeltoe.Discovery.Eureka	90.2%	81.8%
Steeltoe.Discovery.HttpClients	89.9%	91.1%
Steeltoe.Logging.Abstractions	99.4%	95.6%
Steeltoe.Logging.DynamicConsole	100%	92.3%
Steeltoe.Logging.DynamicSerilog	99.1%	95.4%
Steeltoe.Management.Abstractions	100%	100%
Steeltoe.Management.Endpoint	95.9%	86.9%
Steeltoe.Management.GitProperties.Build	95.2%	83.9%
Steeltoe.Management.Prometheus	96.8%	81.2%
Steeltoe.Management.Tasks	95.2%	80%
Steeltoe.Management.Tracing	100%	75%
Steeltoe.Security.Authentication.JwtBearer	100%	95.6%
Steeltoe.Security.Authentication.OpenIdConnect	87.8%	77.2%
Steeltoe.Security.Authorization.Certificate	96.8%	66.6%
Steeltoe.Security.DataProtection.Redis	100%	****

[TimHess]

Thanks for chasing down these resource links, LGTM

[bart-vmware]

I had to rebase, nothing changed since approval.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.4% Duplication on New Code

See analysis details on SonarQube Cloud