Enhancement: enhance bb shell (interactive) mode to share state/memory to improve speed of subsequent commands

[mbrown9764]

From IRC conversation:

1. does the bb shell mode prevent the initial delay of the bb commands?

kergoth: right now it doesn't, since each command is a separate executable script, they don't share anything in memory. of course, after the first, it's pulling from cache, but there's still an extra delay, no performance benefit to the interactive mode right now. we need to think about how to fix that. one way would be to push more of the command handling back into the bitbake daemon process and let the commands use the bitbake server.

[kergoth]

This should be addressed without us having to do anything once Paul Eggleton gets his contrib/paule/tinfoil2 branch merged, which changes the tinfoil bitbake module that we're using to automatically use the bitbake server behind the scenes. Then we could just arrange to source oe-init-build-env-memres rather than oe-init-build-env, which uses the memory resident bitbake server, which lets any bitbake commands use a memory resident server rather than spawning a new one each time. So this will be nice, but it's blocked pending the merge of that.