Add custom XML tool format parser for <tool><action>...</action><object>...</object><properties>...</properties></tool>

The model was generating tool calls in this format:
<tool>
<action>search</action>
<object>financial_data</object>
<properties>
  <query>...</query>
</properties>
</tool>

Added parser support in ApexBig50Parser and strip_tool_calls_from_content
to handle this custom format.