kernel: make LOCALVERSION consistent between recipes

kernel: make LOCALVERSION consistent between recipes

The initial fix for localversion setting in 6.3+ broke older
recipes and also broke recipes setting localversion in a kernel
recipe, as make-mod-scripts (and other locations) can trigger
a regeneration of files and don't have access to the variable.

Moving the setting of this variable to the global namespace
doesn't make sense, so we follow the example of the kernel-abiversion
and save a kernel-localversion to the build artifacts.

Recipes that may regenerate scripts/dynamic files, must
depend on the do_shared_workedir of the kernel and use the helper
function to read the file storing the localversion.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>