Terminal pty size is not initialized

[Tyriar]

I believe after splits was implemented the initial size of the pty is not being set. This means that wrapping could look wrong for the first few lines before a resize is performed (after attachToElement is called).

[Tyriar]

Since split terminals were added the container has not been set when terminals are created, this means that ptys get intiialized with 80 columns which can cause some weird wrapping. The right fix for this is tricky after the introduction of split terminals.

[Tyriar]

We could defer the creation of all terminal processes until the container is visible if we know it's going to be visible. We can even cover most cases where the terminal is not visible such as created via extension host by caching the dimensions (there was some code that did this pretty well before splits was added).