[BUG] Parsing of tool calls does not support arrays in the "arguments"

[bwilliams2]

Describe the bug
The current regex pattern used for parsing tool calls results in an incomplete parsing when nested objects are used within the tool call definition. This severely limits the usefulness of tool calls within Prompty since any arguments with nested objects break parsing.

Relevant code:

promptflow/src/promptflow-core/promptflow/core/_prompty_utils.py

Lines 656 to 657 in 96dbf33

	pattern = r"\n*#{0,2}\s*tool_calls\s*:\s*\n+\s*(\[.*?\])"
	match = re.search(pattern, role_prompt, re.DOTALL)

How To Reproduce the bug
Successful parsing

from promptflow.core._prompty_utils import try_parse_tool_calls

role_prompt = \
"""
## tool_calls: 
[{
    "id": "call_dks134",
    "type": "function",
    "function": { 
        "name":"update",
        "arguments": '{"items": {"name": "test_name"}}'
    }
}]
"""
success = try_parse_tool_calls(role_prompt)

Match group from try_parse_tool_calls

'[{\n    "id": "call_dks134",\n    "type": "function",\n    "function": { \n        "name":"update",\n        "arguments": \'{"items": {"name": "test_name"}}\'\n    }\n}]'

Unsuccessful parsing with inclusion of `]` in the arguments property.
```python
bugged_role_prompt = \
"""
## tool_calls: 
[{
    "id": "call_dks134",
    "type": "function",
    "function": { 
        "name":"update",
        "arguments": '{"items": [{"name": "test_name"}]}'
    }
}]
"""
bugged = try_parse_tool_calls(bugged_role_prompt)

Match group from try_parse_tool_calls

'[{\n    "id": "call_dks134",\n    "type": "function",\n    "function": { \n        "name":"update",\n        "arguments": \'{"items": [{"name": "test_name"}]'

The bugged match group ends at the closing of the "items" property rather than the full tool call definition.

Expected behavior
Tool call definitions with arrays in arguments are correctly parsed.

Running Information(please complete the following information):

• Promptflow Package Version using pf -v: 1.11.0
• Operating System: MacOS Sonoma 14.5
• Python Version using python --version: python==3.12.3

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