IDLE: In the shell, when a long line of output is written progressively, there is a big delay

I'm splitting this issue out of the discussion for issue #42973. Specifically, this comment by @mlouielu mentions:

Besides warping text, there has a performance issue inside the RPCServer and Client.

The (console, write, (text, file), {}) command is sent by server asynccall->putmessage. It should be sent by chunk size to client, and render on IDLE shell.

The result is performed as sent by chunk size, but the client will gather all chunk until it receives all data, then render on IDLE shell.

This cause the shell seems like hanging there, and doing nothing (in REPL, it will output the long string to stdout and so on).

We can manually detect this then manully chunk out (console, write, args, kwargs) command's args size, so that it will look like not hanging there.

The attach patch is a PoC about this.

Start with the linked discussion for issue #42973 and the IDLE RPCServer and Client handling of console write messages. Reproduce a long line written progressively, then verify that chunked output is rendered incrementally instead of waiting for all data to arrive.