Internalise HTTP extensions (remove dependency on HTTPlease)

[tintoy]

As discussed in #165, copy a minimum subset of functionality (e.g. URI templates, and consistent request/response handling) into dotnet-kube-client (e.g. in the KubeClient assembly under the KubeClient.Http namespace) to maintain source-level compatiblity (although not binary compatibility).

Where possible, use existing .NET extensions

Initial targeting should be for net6.0, net7.0, net8.0, net9.0.

Some initial notes

Possible (partial) replacement (of implementation) for HTTPlease URI-template functionality:

• https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.extensions.urihelper?view=aspnetcore-6.0
• https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.extensions.querybuilder?view=aspnetcore-6.0

(note: these look impractical to consume, since the only way to get access to them would require a <FrameworkReference Include="Microsoft.AspNetCore.App" /> from the KubeClient project that uses them)

Alternative implementation (and one of the most popular) of URI templates:

https://github.com/tavis-software/Tavis.UriTemplates