Add possibility to add AWS services to DI with a key

[OleksiiZuiev]

Description

Add the possibility to add AWS services to DI with a key, utilizing Keyed services feature of the framework.

The change relies on the framework feature that was introduced in .NET8. If target framework is 8, newer dependencies of Microsoft.Extensions.DependecyInjection , Microsoft.Extensions.DependencyInjection.Abstractions are referenced and extention methods to IServiceCollection are added.

AddKeyedAwsService and TryAddKeyedAwsService are added with 2 overloads for each, to align with extension methods that add services without a key.

Motivation and Context

This feature allows to add multiple registrations of a single service type. This enables cases when different instances of a service need to have different AWS options. One of the cases is described in issue #3561

Testing

I extended DependencyInjectionTests in NETCore.SetupTests and ensured they all pass.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have read the README document
• I have added tests to cover my changes
• All new and existing tests passed

License

• I confirm that this pull request can be released under the Apache 2 license

[normj]

Thanks for the PR. Looks good.

[normj]

Merging after pulling in branch and successfully running internal full build against the branch.