mtm.ts - _send method - parametrized chunk size

[TortoiseMax]

Sending a large .psl file to host takes a lot of time e.g. a file that has 500kB takes ~30 seconds.
Whereas transferring a similar file via ftp takes 1 second.
This is partially due to dividing a file into 1024 chunks in the _send() method of the mtm.ts class.
Because of a 1kB chunk size, for a sample file that has 500kB it takes ~500 MRPC121 calls to transfer a file to a host.

Having a vscode-psl level parameter to control chunk size (with the existing default value of 1024) may not cure situation right away, but would allow for experimentation and fine-tuning of the send function. Hopefully, eventually this will lead to shorter upload times.