A collection of updates to the importnb interface

[tonyfast]

importnb has lacked attention for a while. this pull request brings some much needed care.

• reduce the complexity of the Notebook mro. remove several errant intermediate classes
• the tests has a lot of creep from testing new features over time. we cull this mess and write more explicit tests with less test notebooks.
• we continue our transition to hatch.

[tonyfast]

yikes that took at lot of annoying work at the end. this test suite is pretty big which catches different things and that is good. the tail problem though was a nuance that didn't really change the behavior of importnb.

the Notebook api interface got a massive overhaul in the pr. it is easier to invoke command line programs and overload the existing behavior. we removed redudandancy in the creation of the hook finder.

im very happy with hatch and how it centralizes a lot of different dev tooling into a single configuration. less files. less entropy.