The Xcode 15.4 Release Candidate (RC) image has been released on M1 resource class and can be selected as follows:
macos:
xcode: 15.4.0
Xcode 15.4 RC Release Notes | Apple Developer Documentation
Apple Silicon VM Image Info
Xcode 15.4 RC Build version 15F31c
is installed at /Applications/Xcode-15.4.app
The full manifest of installed software can be found here