fix(chat): Fix ChatStream error caused by tool error

[jguoamz]

Problem

• Sometimes we receive error in sendAIResponse where await ToolUtils.queueDescription(tool, chatStream) throws error and we don't handle it currently
• Minor refactoring to remove tool-unavailble custom action and processUnavailableToolUseMessage to re-use processToolUseMessage instead

Solution

• Store the error along with toolUse in chatSession so that we can handle it correctly in processToolUseMessage

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[github-actions]

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