[WIP] many: support multi-volume gadget asset updates

[anonymouse64]

This PR serves as a historical collection of all PRs to implement the feature of implementing multi-volume gadget asset updates for UC20+. Everything here is proposed in additional PR's too, so this can eventually be closed.

PRs:

• [x] https://github.com/snapcore/snapd/pull/10903
• [x] https://github.com/snapcore/snapd/pull/10904
• [x] https://github.com/snapcore/snapd/pull/10905
• [x] https://github.com/snapcore/snapd/pull/10916
• [x] https://github.com/snapcore/snapd/pull/10917
• [x] https://github.com/snapcore/snapd/pull/10918
• [x] https://github.com/snapcore/snapd/pull/10919
• [x] https://github.com/snapcore/snapd/pull/10920
• [x] https://github.com/snapcore/snapd/pull/10921
• [x] https://github.com/snapcore/snapd/pull/10979
• [x] https://github.com/snapcore/snapd/pull/11021
• [x] https://github.com/snapcore/snapd/pull/11022
• [x] https://github.com/snapcore/snapd/pull/11028 (for ICE merge compatibility)
• [x] https://github.com/snapcore/snapd/pull/11035 (for ICE merge compatibility)
• [x] https://github.com/snapcore/snapd/pull/11043
• [x] https://github.com/snapcore/snapd/pull/11060
• [x] https://github.com/snapcore/snapd/pull/11070
• [x] https://github.com/snapcore/snapd/pull/11084
• [x] https://github.com/snapcore/snapd/pull/11127
• [x] https://github.com/snapcore/snapd/pull/11154
• [x] https://github.com/snapcore/snapd/pull/11207
• [x] https://github.com/snapcore/snapd/pull/11219
• [x] https://github.com/snapcore/snapd/pull/11220
• [x] https://github.com/snapcore/snapd/pull/11229
• [x] https://github.com/snapcore/snapd/pull/11230
• [x] https://github.com/snapcore/snapd/pull/11234
• [x] https://github.com/snapcore/snapd/pull/11235
• [x] https://github.com/snapcore/snapd/pull/11296
• [x] https://github.com/snapcore/snapd/pull/11297
• [x] https://github.com/snapcore/snapd/pull/11331
• [x] https://github.com/snapcore/snapd/pull/11332
• [x] https://github.com/snapcore/snapd/pull/11333
• [x] https://github.com/snapcore/snapd/pull/11334
• [x] https://github.com/snapcore/snapd/pull/11335
• [x] https://github.com/snapcore/snapd/pull/11354
• [x] https://github.com/snapcore/snapd/pull/11374
• [x] https://github.com/snapcore/snapd/pull/11384
• [x] https://github.com/snapcore/snapd/pull/11414
• [x] https://github.com/snapcore/snapd/pull/11415
• [x] https://github.com/snapcore/snapd/pull/11420
• [x] https://github.com/snapcore/snapd/pull/11433
• [ ] https://github.com/snapcore/snapd/pull/11494
• [ ] https://github.com/snapcore/snapd/pull/11573
• [ ] https://github.com/snapcore/snapd/pull/11580

[codecov-commenter]

Codecov Report

Merging #10906 (1003de2) into master (2bedfe6) will decrease coverage by 0.27%. The diff coverage is 74.19%.

@@            Coverage Diff             @@
##           master   #10906      +/-   ##
==========================================
- Coverage   78.24%   77.96%   -0.28%     
==========================================
  Files         935      939       +4     
  Lines      108436   109906    +1470     
==========================================
+ Hits        84846    85691     +845     
- Misses      18301    18893     +592     
- Partials     5289     5322      +33     

Flag	Coverage Δ
unittests	77.96% <74.19%> (-0.28%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
gadget/device_linux.go	100.00% <ø> (+3.46%)	:arrow_up:
gadget/update.go	85.92% <74.19%> (-1.89%)	:arrow_down:
daemon/api_quotas.go	75.00% <0.00%> (-5.56%)	:arrow_down:
boot/reboot.go	65.21% <0.00%> (-4.56%)	:arrow_down:
cmd/snap-preseed/main.go	73.33% <0.00%> (-4.28%)	:arrow_down:
snap/quota/quota.go	94.83% <0.00%> (-2.20%)	:arrow_down:
wrappers/services.go	39.48% <0.00%> (-2.14%)	:arrow_down:
overlord/configstate/configcore/services.go	71.32% <0.00%> (-1.53%)	:arrow_down:
interfaces/systemd/backend.go	65.87% <0.00%> (-1.35%)	:arrow_down:
overlord/devicestate/handlers_install.go	66.46% <0.00%> (-1.05%)	:arrow_down:
... and 45 more

:mega: Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[anonymouse64]

It seems the final commit to try and enable the special device with the weird kernel is actually breaking native UC20 on GCE, I see this in the serial console where it gets stuck:

Jan 09 14:53:09 ubuntu snapd[1347]: partition.go:295: partition rescan file /sys/devices/pci0000:00/0000:00:03.0/virtio0/host0/target0:0:1/0:0:1:0/block/sda/device/rescan for device /dev/sda exists, so using it to reload partition table instead of partx
Jan 09 14:53:14 ubuntu snapd[1347]: taskrunner.go:271: [change 2 "Setup system for run mode" task] failed: cannot install system: cannot create the partitions: partition not available: device /dev/sda3 not available