[8.0] Update Ubuntu pipelines from 18.04 to 22.04

[carlossanlop]

All these 18.04 pipelines consistently fail in 8.0 with BadExit due to operation not permitted to write to disk. Example: https://github.com/dotnet/runtime/pull/113328/checks?check_run_id=38659577258

Per @richlander 's recommendation, I'm updating these to the minimum supported, 22.04.

I also opened an Arcade PR for common files: dotnet/arcade#15630

[Copilot]

Pull Request Overview

This PR updates Ubuntu pipeline configurations from 18.04 to 22.04 to address write permission issues observed in the 8.0 release.

• Update pipeline image demands and labels to reflect Ubuntu 22.04.
• Modify Helix queue configurations for both coreclr and libraries pipelines.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
eng/pipelines/common/xplat-setup.yml	Updated image demand from Build.Ubuntu.1804.Amd64.Open to Build.Ubuntu.2204.Amd64.Open.
eng/pipelines/coreclr/templates/helix-queues-setup.yml	Updated Ubuntu label for browser wasm and Linux arm setups, but docker image tag remains unchanged.
eng/pipelines/libraries/helix-queues-setup.yml	Updated Ubuntu label for ARM64 setup; docker image tag still references ubuntu-18.04.

Comments suppressed due to low confidence (3)

eng/pipelines/coreclr/templates/helix-queues-setup.yml:55

• The Docker image tag still references 'ubuntu-18.04' while the label has been updated to Ubuntu.2204. Please confirm if the image tag also needs to be updated to ensure consistency.

- - (Ubuntu.2204.Amd64.Open)mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-helix-webassembly

eng/pipelines/coreclr/templates/helix-queues-setup.yml:68

• The Docker image tag for the ARM32 setup continues to indicate 'ubuntu-18.04'. Confirm if this should be updated to align with the 22.04 label.

- - (Ubuntu.2204.Arm32.Open)Ubuntu.2204.Armarch.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-helix-arm32v7

eng/pipelines/libraries/helix-queues-setup.yml:43

• The Docker image tag still shows 'ubuntu-18.04' for the ARM64 setup. Please verify if this inconsistency is intentional or if an update is needed.

- - (Ubuntu.2204.Arm64.Open)Ubuntu.2204.ArmArch.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-helix-arm64v8

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/runtime-infrastructure
See info in area-owners.md if you want to be subscribed.

[carlossanlop]

I'd also like to get a review for my arcade PR: dotnet/arcade#15630

[carlossanlop]

/ba-g timeouts in windows, unrelated to this change