Fix replacing for variables

[Sy0xFF]

Motivation and Context

We had a problem with SKFunctionInput when these are arrays. For example, the output was [$variable1,$variable2]. These were not replaced with the actual values.

Description

Replaced the logic to only get one variable with a regex solution to replace all variables in the inner text. Now all values will be replaced correctly.

Contribution Checklist

• [x] The code builds clean without any errors or warnings
• [x] The PR follows SK Contribution Guidelines (https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
• [x] The code follows the .NET coding conventions (https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions) verified with dotnet format
• [x] All unit tests pass, and I have added new tests where possible (excluding unrelated already broken unit tests)
• [x] I didn't break anyone :smile:

[Sy0xFF]

@microsoft-github-policy-service agree

[lemillermicrosoft]

Thanks for the PR @Sy0xFF -- we're in the process of refactoring things here, see https://github.com/microsoft/semantic-kernel/pull/523. I'll incorporate this fix with those changes.

[dluc]

as per @lemillermicrosoft the fix will be integrated into #523