gnu: ungoogled-chromium: Update to 83.0.4103.106-0.f08ce8b [security fixes].

This fixes CVE-2020-6465, CVE-2020-6466, CVE-2020-6467, CVE-2020-6468,
CVE-2020-6469, CVE-2020-6470, CVE-2020-6471, CVE-2020-6472, CVE-2020-6473,
CVE-2020-6474, CVE-2020-6475, CVE-2020-6476, CVE-2020-6477, CVE-2020-6478,
CVE-2020-6479, CVE-2020-6480, CVE-2020-6481, CVE-2020-6482, CVE-2020-6483,
CVE-2020-6484, CVE-2020-6485, CVE-2020-6486, CVE-2020-6487, CVE-2020-6488,
CVE-2020-6489, CVE-2020-6490, CVE-2020-6491, CVE-2020-6493, CVE-2020-6494,
CVE-2020-6495, CVE-2020-6496, CVE-2020-6497, and CVE-2020-6498.

* gnu/packages/patches/ungoogled-chromium-system-jsoncpp.patch,
gnu/packages/patches/ungoogled-chromium-system-zlib.patch: New files.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/chromium.scm (%preserved-third-party-files): Adjust for 83.
(%chromium-version): Set to 83.0.4103.106.
(%ungoogled-revision): Set to f08ce8b3f1300ef0750b5d6bf967b9cbbfd9a56d.
(%gentoo-revision, %gentoo-patches, %debian-patches): New variables.
(gentoo-patch, debian-patch): New procedures.
(%chromium-origin, %ungoogled-origin): Update hashes.
(ungoogled-chromium-source): Don't apply patches from %DEBIAN-ORIGIN, but take
%GENTOO-PATCHES, %DEBIAN-PATCHES, and the local patch files.
(ungoogled-chromium)[arguments]: Remove "enable_swiftshader=false" from
 #:configure-flags.  Add "icu_use_data_file=false".  Set CFLAGS in phase.
Remove obsolete substitution.  Adjust install phase to install .so files for
ANGLE and Swiftshader.
[native-inputs]: Change from CLANG-9 to CLANG-10.
[inputs]: Replace ICU4C with ICU4C-67.
(ungoogled-chromium/wayland): Remove obsolete substitution.  Add
"ozone_platform_x11=true" in #:configure-flags.