src/poky:package: export debugsources in PKGDESTWORK as json

The source information used during packaging can be use from other tasks to
have more detailed information on the files used during the compilation and
improve SPDX accuracy.

Source files used during compilation are store as compressed zstd json in
pkgdata/debugsources/$PN-debugsources.json.zstd
Format:
{ binary1: [src1, src2, ...], binary2: [src1, src2, ...] }

I checked the sstate size, and it slightly increases using core-image-full-cmdline:
without patch: 2456792 KB sstate-cache/
with patch:    2460028 KB sstate-cache/
(4236 KB or 0.17%)

CC: Richard Purdie <richard.purdielinuxfoundation.org>
(From OE-Core rev: c507dcb8a8780a42bfe68b1ebaff0909b4236e6b)

Signed-off-by: Daniel Turull <daniel.turullericsson.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briandbootlin.com>
Signed-off-by: Richard Purdie <richard.purdielinuxfoundation.org>

Author: danielturull