Clarify how to verify SGX evidence without an Intel SGX-enabled platform (#3158)

This PR encompasses two complementing purposes:

A documentation on verifying an Intel SGX evidence as produced by WAMR,
including a guide for verification without an Intel SGX-enabled platform.
This also contains a small addition to the RA sample to extract specific
information, such as whether the enclave is running in debug mode.

A C# sample to verify evidence on trusted premises (and without Intel SGX).
Evidence is generated on untrusted environments, using Intel SGX.

samples/sgx-ra/non-sgx-verify/csharp/README.md

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+# Examples of evidence verification without Intel SGX using C#
+This sample demonstrates how to validate WAMR-generated evidence without using an Intel SGX-enabled platform.
+A typical use case is a Web service hosted on trusted premises.
+
+## Prerequisites
+ - [dotnet-sdk](https://learn.microsoft.com/en-us/dotnet/core/install/linux) (8+)
+ - [librats](https://github.com/inclavare-containers/librats)
+ - Intel infrastructure for validating evidence, [see here](../../README.md#validate-quotes-on-non-sgx-platforms)
+
+This sample has been tested on Linux Ubuntu 20.04+.
+Any other Linux platforms should be supported.
+This sample should also work on other OS, provided librats can be compiled on those other OS.
+
+## How to use
+ - Supply the reference values to consider trustworthy in [Program.cs](Program.cs#L15-L27).
+ - Generate a valid JSON evidence using WAMR on an Intel SGX-enabled platform.
+ - Fill in the JSON evidence in [Program.cs](Program.cs#L28).
+ - Run the command `dotnet run` in this directory.