new EESSI version, incl. new compat layer (2025.06)

We should determine when we will create a new compat version version in software.eessi.io.

Potential good reasons could include:

• new to update to a new glibc package
• starting to use EasyBuild v5.0
• new toolchains (like upcoming foss/2024a)
• change in design decisions (would be useful w.r.t. GPU support)