cooker: Drop unused variables from collect_bbfiles()

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Separate out collections handling code into its own class

The Cooker class is too large and needs to be split up into different
functional units. Splitting out the collections code into its own class
seems like a good place to start to try and disentangle things.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Fix get_bbfiles()

Its clear looking at the code the path argument has never been used and doesn't
work. Tweak the function to be a little more readable.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Remove pointless repeated import

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker.py: Drop confusing updateCache calls

updateCache() gets called by command.py when needed and needs to be iterated
over. The calls in cooker.py are therefore just plain wrong/confusing now.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Drop pointless variables

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Rename confusing buildDepgraph task to handlePrefProviders

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Rename status variable to recipecache

"status" is a relic of very early versions of bitbake, rename it to match what it now
means.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>