Python: Allow enums to be passed in to on_function_result. Improve handling FRC result so it can be hashed.

[moonbox3]

Motivation and Context

Two topics in this PR:

• A request to be able to pass in Enums to the Python process on_function_result, instead of just strings.
• There were some custom types (Pydantic models) that were unable to hash during an agent group chat. One could mark the model frozen so that it is hashable; however, we should add better handling in our code, in case a dev doesn't want to do that.

Description

This PR:

• checks if the function name in on_function_result in our process framework is an enum, if so, convert to a string.
• improves the parsing of the result in FunctionResultContent so that it can be included in the hash function during an agent group chat. Adding tests to handle multiple different scenarios.
• Closes Python: unhashable type exception for custom return type in kernel function #10299
• Closes Process Framework on_function_result requires string, not enum or string #10305

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel/processes
process_step_builder.py	110	24	78%	45, 94, 108, 115–128, 140–147, 156, 165–175, 180, 220
TOTAL	17069	1833	89%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3042	4 💤	0 ❌	0 🔥	1m 19s ⏱️