patch.bbclass: when the patch fails show more info on the fatal error

There are situations when the user have the 'patchdir' defined
as a parameter on SRC_URI. However he doesn't know that with this
the patch is applied relatively to the receipe source dir 'S'.

- When user have 'patchdir' defined check if this directory exist.
- If the patch fails show addition info to the user:
  - Import: show the striplevel
  - Resolver: show the expanded 'patchdir' to the user.

The next example is from opencv in meta-oe layer, here the
patch is applied on the target directory ${WORKDIR}/git/contrib.

S = "${WORKDIR}/git"
SRCREV_FORMAT = "opencv_contrib"
SRC_URI = "git://github.com/opencv/opencv.git;name=opencv \
           git://github.com/opencv/opencv_contrib.git;destsuffix=contrib;name=contrib \
           file://0001-sfm-link-with-Glog_LIBS.patch;patchdir=../contrib

 \
           "

* When the patch fail there are no message that indicates the real reason.
  patchdir=../no-found-on-file-system

ERROR: opencv-4.5.2-r0 do_patch: Command Error: 'quilt --quiltrc /build/tmp/work/core2-64-poky-linux/opencv/4.5.2-r0/recipe-sysroot-native/etc/quiltrc push' exited with 0  Output:
stdout: Applying patch 0001-sfm-link-with-Glog_LIBS.patch
can't find file to patch at input line 37
Perhaps you used the wrong -p or --strip option?

* The check of the patchdir will add a new fatal error
  when the user specifies a wrong path than don't exist.
  patchdir=../no-found-on-file-system

ERROR: opencv-4.5.2-r0 do_patch: Target directory '/build/tmp/work/core2-64-poky-linux/opencv/4.5.2-r0/git/../no-found-on-file-system' not found, patchdir '../no-found-on-file-system' is incorrect in patch file '0001-sfm-link-with-Glog_LIBS.patch'

* When we can't aplly the patch but the patchdir exist,
  show the expanded patchdir on fatal error.
  patchdir=../git

ERROR: opencv-4.5.2-r0 do_patch: Applying patch '0001-sfm-link-with-Glog_LIBS.patch' on target directory '/build/tmp/work/core2-64-poky-linux/opencv/4.5.2-r0/git/../git'
Command Error: 'quilt --quiltrc /build/tmp/work/core2-64-poky-linux/opencv/4.5.2-r0/recipe-sysroot-native/etc/quiltrc push' exited with 0  Output:
stdout: Applying patch 0001-sfm-link-with-Glog_LIBS.patch
can't find file to patch at input line 37
Perhaps you used the wrong -p or --strip option?

Signed-off-by: Jose Quaresma <quaresma.jose@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>