[Alpine 3.21] Add infrastructure support for new OS version

[ashnaga]

• Helix image support: Add Alpine 3.21 helix images dotnet-buildtools-prereqs-docker#1282
• [For non-Docker] Make the new OS Version available in the Helix pools
• Check for any hardware updates
• Check if new hardware needs to be added to the infra pool for support

[ilyas1974]

Created dotnet/dnceng#4348 to track this work