Fix MTP command-line parsing

[Youssef1313]

It's not correct to consider space as an option-value delimiter.

Fixes #7039

The implementation was previously buggy, and unnecessarily more complicated.

This simplifies the implementation, and makes it more correct.

[nohwnd]

Can you please explain here, or in the linked issue what is the problem that is solved, and why it is not correct to consider space as delimiter? I am sure someone will run into this in the future, and it is complicated to figure out what is the intention of this change from the code alone.

[Youssef1313]

In command line, when you type --option value, they end up as two separate arguments (i.e, you have args array of two elements, --option and value. You don't end up with --option value as a single arg. You can end up with --option value as single arg if you enclose it in double quotes in command-line, and in which case I don't think splitting by the space is correct here.

The rest of the logic, as indicated in the linked issue, is already also broken as it can swallow some values. Revising the whole logic, lots of things don't make sense.