Render `newshape` `text` and `texttemplate` during initial shape draw

[emilykl]

Currently, if a shape label is defined in newshape using text or texttemplate, the text is not rendered until mouseup following the initial draw.

Modify shape drawing code such that the text is rendered during mousedown.

This is doable, but involves some additional complexity since the initial shape drawing code (during mousedown) is completely separate from the normal shape drawing code, and we don't have access to the same set of variables.

Implementation will involve modifying key lines in src/components/selections/select.js and possibly src/components/shapes/display_outlines.js due to the overlap between selection and shape code.