Unpin arm build image, use Debian 12 helix images (dotnet#102059)

Reverts the temporary fix from
dotnet#102035, and switches to
Debian 12 arm images added in
dotnet/dotnet-buildtools-prereqs-docker#1041
for testing.

This replaces the Ubuntu 18.04 arm images with Debian because
building new Ubuntu 22.04 arm images is blocked on
dotnet/dnceng#2808.

Fixes dotnet#102030

eng/pipelines/common/templates/pipeline-with-resources.yml

@@ -17,7 +17,7 @@ extends:
 
     containers:
       linux_arm:
-        image: mcr.microsoft.com/dotnet-buildtools/prereqs:azurelinux-3.0-cross-arm-net9.0-20240507035943-1390eea
+        image: mcr.microsoft.com/dotnet-buildtools/prereqs:azurelinux-3.0-cross-arm-net9.0
         env:
           ROOTFS_DIR: /crossrootfs/arm
 

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

@@ -63,9 +63,9 @@ jobs:
     # Linux arm
     - ${{ if eq(parameters.platform, 'linux_arm') }}:
       - ${{ if eq(variables['System.TeamProject'], 'public') }}:
-        - (Ubuntu.1804.Arm32.Open)Ubuntu.2004.Armarch[email protected]/dotnet-buildtools/prereqs:ubuntu-18.04-helix-arm32v7
+        - (Debian.12.Arm32.Open)Ubuntu.2004.ArmArch[email protected]/dotnet-buildtools/prereqs:debian-12-helix-arm32v7
       - ${{ if eq(variables['System.TeamProject'], 'internal') }}:
-        - (Ubuntu.1804.Arm32)Ubuntu.2004.Armarch@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-helix-arm32v7
+        - (Debian.12.Arm32)Ubuntu.2004.ArmArch@mcr.microsoft.com/dotnet-buildtools/prereqs:debian-12-helix-arm32v7
 
     # Linux arm64
     - ${{ if eq(parameters.platform, 'linux_arm64') }}:

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

@@ -26,7 +26,7 @@ jobs:
     # Linux arm
     - ${{ if eq(parameters.platform, 'linux_arm') }}:
       - ${{ if or(eq(parameters.jobParameters.isExtraPlatformsBuild, true), eq(parameters.jobParameters.includeAllPlatforms, true)) }}:
-        - (Debian.11.Arm32.Open)[email protected]/dotnet-buildtools/prereqs:debian-11-helix-arm32v7
+        - (Debian.12.Arm32.Open)[email protected]/dotnet-buildtools/prereqs:debian-12-helix-arm32v7
 
     # Linux armv6
     - ${{ if eq(parameters.platform, 'linux_armv6') }}: