2.7.4: Update Microsoft.WSL.Kernel to 6.18.26.1 (#40161)

• 
  

  Update Microsoft.WSL.Kernel to 6.18.26.1-1

  
  


• 
  

  Update tests for Linux 6.18 kernel behavior changes

  
  

Adjust eventfd size validation, lxtfs writev, and mount option

format expectations to match 6.18 kernel behavior.

• Update test patterns for new kernel /proc/mounts cache format

The kernel now outputs cache=0x5 (hex) instead of cache=5 (decimal) in

/proc/mounts for 9p filesystems. Update the ExpectMount patterns in

WSLCTests::WindowsMounts and WSLCTests::GPU to match the new format.

Co-authored-by: Ben Hillis [email protected]

Co-authored-by: Copilot [email protected]