Fix environment variable when contains URI with splitter sign = inside

[jkljajic]

Fixes #.
When OTEL_RESOURCE_ATTRIBUTES contains KeyValuePair key=http://localhost/key=value&key2=value2 it does not detect very well because it splits with "=" and get more then length of 2

Changes

#if NET6_0 || NETSTANDARD2_1_OR_GREATER
                string[] keyValuePair = rawKeyValuePair.Split(AttributeKeyValueSplitter,2);
#else
                string[] keyValuePair = rawKeyValuePair.Split(AttributeKeyValueSplitter);
                if(keyValuePair.Length > 2)
                {
                    keyValuePair = new string[] { keyValuePair[0], string.Join(AttributeKeyValueSplitter.ToString(), keyValuePair.Skip(1)) };
                }
#endif

Please provide a brief description of the changes here.

trying to spit only on the first occurrence of AttributeKeyValueSplitter and because that is supported in net6 and NETSTANDARD2_1_OR_GREATER I need to add additional work around wor previus Dotnet release

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

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[reyang]

It's unclear how OTEL_RESOURCE_ATTRIBUTES should be used when the attribute value has special characters (any escape rules), is there a clear spec or the spec is simply buggy?

[jkljajic]

It's unclear how OTEL_RESOURCE_ATTRIBUTES should be used when the attribute value has special characters (any escape rules), is there a clear spec or the spec is simply buggy?

Is not point to any special character its just splitter '=', in our case we trying to inject a log URL reference to Grafana or any other tool and call directly, using the same approach with Java agent that works and we see that the same URL in open telemetry traces, but not in case Dotnet.
I think this is just overseeing and should be good that parsing key-value pairs keep that in mind and allow to use of the splitter sign in the value part.

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[reyang]

Here goes the requirement from the spec: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md#specifying-resource-information-via-an-environment-variable