devtool: provide support for devtool menuconfig command

devtool: provide support for devtool menuconfig command

All packages that support the menuconfig task will be able to run
devtool menuconfig command. This would allow the user to modify the
current configure options and create a config fragment which can be
added to a recipe using devtool finish.

1. The patch checks if devtool menuconfig command is called for a valid
package.
2. It checks for oe-local-files dir within source and creates one if
needed, this directory is needed to store the final generated config
fragment so that devtool finish can update the recipe.
3. Menuconfig command is called for users to make necessary changes.
After saving the changes, diffconfig command is run to generate the
fragment.

Syntax:
	devtool menuconfig <package name>
	 Ex: devtool menuconfig linux-yocto

The config fragment is saved as devtool-fragment.cfg within
oe-local-files dir.

	Ex:
<workspace_path>/sources/linux-yocto/oe-local-files/devtool-fragment.cfg

Run devtool finish to update the recipe by appending the config fragment
to SRC_URI and place a copy of the fragment within the layer where the
recipe resides.
	Ex: devtool finish linux-yocto meta

[YOCTO #10416]

Signed-off-by: Sai Hari Chandana Kalluri <chandana.kalluri@xilinx.com>
Signed-off-by: Alejandro Enedino Hernandez Samaniego <alejandr@xilinx.com>
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>