flatpak: use container resolver to resolve flatpak refs

[lzap]

We need to optimize memory consumption and we ideally want to do this just once, for container refs. Flatpak did have its own resolver, let's reuse what we have.

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Initially I wanted to solve the memory problem described here: osbuild/image-builder-cli#514

Only to figure out that fedora registry does not support server-side filtering, at least not the one we need here. I think we really need to optimize the parsing. I believe @achilleas-k has some ideas already.

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Update: I did have one idea which was confirmed - aren't we querying the same image over and over again just with different inputs? And this was confirmed. A simple patch (2nd commit) that implements a trivial "cache" shaves the processing time significantly. It just remembers the last tag and parsed data so it can be immediately reused, no need for fancy LRU caching or something like that.

Before:

time go run ./cmd/image-builder -v manifest --distro fedora-44 silverblue-installer
real	2m44.135s
user	0m21.812s
sys	0m9.427s

After:

time go run ./cmd/image-builder -v manifest --distro fedora-44 silverblue-installer
real	0m49.459s
user	0m10.343s
sys	0m4.078s

Now, I really hope this is not just quay.io being slow for me, please test this too :-)

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Reminder for myself: rebase after osbuild/osbuild-composer#5136 and osbuild/osbuild-composer#5138

[supakeen]

Looks good to me to re-use the existing code for this instead of the one I duplicated; needs linter appeasement.

[achilleas-k]

Good stuff, thank you.

LGTM

[achilleas-k]

Nice!!

[lzap]

Also tested memory, is down from 413 MiB to 285 MiB. Before:

	Command being timed: "go run ./cmd/image-builder -v manifest --distro fedora-44 silverblue-installer"
	User time (seconds): 15.90
	System time (seconds): 6.92
	Percent of CPU this job got: 20%
	Elapsed (wall clock) time (h:mm:ss or m:ss): 1:52.87
	Average shared text size (kbytes): 0
	Average unshared data size (kbytes): 0
	Average stack size (kbytes): 0
	Average total size (kbytes): 0
	Maximum resident set size (kbytes): 413000
	Average resident set size (kbytes): 0
	Major (requiring I/O) page faults: 2
	Minor (reclaiming a frame) page faults: 529761
	Voluntary context switches: 268150
	Involuntary context switches: 488
	Swaps: 0
	File system inputs: 0
	File system outputs: 104
	Socket messages sent: 0
	Socket messages received: 0
	Signals delivered: 0
	Page size (bytes): 4096
	Exit status: 0

After:

	Command being timed: "go run ./cmd/image-builder -v manifest --distro fedora-44 silverblue-installer"
	User time (seconds): 4.91
	System time (seconds): 2.09
	Percent of CPU this job got: 15%
	Elapsed (wall clock) time (h:mm:ss or m:ss): 0:43.81
	Average shared text size (kbytes): 0
	Average unshared data size (kbytes): 0
	Average stack size (kbytes): 0
	Average total size (kbytes): 0
	Maximum resident set size (kbytes): 285636
	Average resident set size (kbytes): 0
	Major (requiring I/O) page faults: 0
	Minor (reclaiming a frame) page faults: 189780
	Voluntary context switches: 31028
	Involuntary context switches: 294
	Swaps: 0
	File system inputs: 0
	File system outputs: 104
	Socket messages sent: 0
	Socket messages received: 0
	Signals delivered: 0
	Page size (bytes): 4096
	Exit status: 0