Add Texas PHP0048E_HTQFP-48

Required by symbol MR: kicad-symbols!1719 (closed)

DS: https://www.ti.com/lit/ds/symlink/tusb4020bi.pdf#page=42

Notable feature: large thermal pad (much larger than EP) with an EP-sized solder mask opening:

Also includes a tweak to the generator to allow parts to override the device_type field.

Questions I have:

• I put it in the TQFP file, though TI calls it an HTQFP, the H meaning "thermally enhanced". But some TQFPs already have EPs.
• The DS expects 100% coverage - is this something to obey, even though it'll cover the vias?