check desn't catch a problem that prevents cascade filter from running

[jepler]

Background: In adafruit/circuitpython#5519 a revision was made to nvm.toml that just errored when trying to fill out the nvm header template. I wanted to add a check for toml file correctness, and first tried cascadetoml check, but that doesn't find the problem. Only cascadetoml cascade filter (or the equivalent, from Python) seems to do so.

I also don't know for sure whether it should be an error that manufacturer_id appears in both flash/puya/P25Q16H.toml and flash/puya/puya.toml, or if it should be allowed.

[jepler]

Here's the problematic ref in nvm.toml: adafruit/nvm.toml@73cedb3

[tannewt]

It should be an error in check. I like to be strict about where things should be.