Move code related to converting history messages into UI representation
from utils into history/render.lua for better code organization and
clean up the implementation.
Code dealing with scanning history messages and extracting some data or
state belongs to avante/history/ so move it there. Along with the move
update the implementation to make use of get_tool_use_data() and
get_tool_result_data() helpers to simplify it.
Also rename the function to History.get_pending_tools() to better
reflect its purpose: "uncalled" means something that was done without
request, unsolicited, not something that has not completed yet.
There are many places in the code that wants to work with content of
"tool use" and "tool result" messages. Currently such code uses
is_tool_use_message() and is_tool_result() message to check if message
is of right kind, and then pokes into message internals. This is not
very efficient.
Introduce get_tool_use_data() and get_tool_result_data() that would
return contents of the message if it is of right kind, or nil otherwise.
Also introduce get_tool_result() that attempts to locate result of a
tool execution by its invocation ID.
The utils module has grown too big and contains unrelated functionality.
Start moving code related to managing history messages comprising chat
history into lua/avante/history module to keep the code more manageable.
