.Net: Graduate Filters feature

[markwallace-microsoft]

Checklist to be completed when graduating an experimental feature

• [x] Verify the Filters feature is functionality complete (#5436)
• [x] Are we keeping filter properties on the Kernel
• [x] ​Verify API docs are complete and arrange to have them published
• [x] Make appropriate updates to Learn docs​
• [x] Make appropriate updates to Samples​​
• [x] Verify there are no serious open Issues​​
• [x] Verify there are sample implementations​ for the main use cases
• [x] Update table in EXPERIMENTS.md
• [x] Remove SKEXP​ flag from Filters code

[dmytrostruk]

Are we keeping filter properties on the Kernel

Based on comments, filter properties are still useful and adding new type of filters to Kernel type should not be complex: https://github.com/microsoft/semantic-kernel/issues/6085#issuecomment-2090685483.

[dmytrostruk]

Verify API docs are complete and arrange to have them published

• AutoFunctionInvocationContext Class
• IAutoFunctionInvocationFilter Interface
• FunctionInvocationContext Class
• IFunctionInvocationFilter Interface
• IPromptRenderFilter Interface
• PromptRenderContext Class

[dmytrostruk]

Update table in EXPERIMENTS.md Remove SKEXP​ flag from Filters code

https://github.com/microsoft/semantic-kernel/pull/7004