Bump buildroot to 2023.02-rc2 (#2374)

* Update config for Buildroot 2023.02

* Use Buildroot's version of the rtl8821cu package

Buildroot provides a newer driver for the RTL8821CU based chipsets
provided by https://github.com/morrownr/8821cu-20210118.

* Pass argument when verifying partition table

This also avoids running into a segmentation fault in the current
version of sgdisk.

* Remove obsolte GRUB2/NetworkManager patches

* Bump buildroot

* buildroot 90aa1a6daa...4832525e6c (4596):
  > package/runc: add support for CGroup device permission updates
  > package/network-manager: fix build with -Dmodem_manager=false
  > package/dbus-broker: bump to release 33
  > package/iptables: Allow to use iptables with nf_tables backend
  > package/brcmfmac_sdio-firmware-rpi: bump to latest version
  > package/linux-firmware: Deploy fewer Intel WiFi 22000 series variants
  > package/linux-firmware: Add more Intel WiFi 22000 series variants
  > package/linux-firmware: Add Broadcom BNX2 firmware
  > package/rpi-firmware: bump version to 1.20230106
  > Update for 2023.02-rc2

* Use Ubuntu 22.04 for CI checks

* Bump xe-guest-utilities to 7.33.0

* Remove unnecessary shellcheck ignore for xe-guest-utilities

* Address new buildroot check-packages issues

.github/workflows/pr-checks.yml

@@ -6,7 +6,7 @@ on: [pull_request]
 
 jobs:
   linters:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
     - name: Check out code
       uses: actions/checkout@v3
@@ -21,7 +21,7 @@ jobs:
     - name: Check shell scripts
       uses: ludeeus/action-shellcheck@2.0.0
       with:
-        ignore: buildroot buildroot-external/package/xe-guest-utilities
+        ignore: buildroot
 
     - name: Check buildroot-external packages
       run: |