chore(core): Convert luma object to singleton

[ibgreen]

For #

Background

• Convert luma API to a singleton instead of static functions.
• Reduces the amount of global state and makes the code significantly more maintainable.

Differences

• The luma API namespace will now have a prototype field, and that would technically become visible in the script version.
• The browser luma object will now expose not just log and version, but also createDevice etc.

Change List

• As above

Next Steps

• Move the luma.gl init.ts code into the Luma singleton.