bump ramdisk to 1200MB

[iliana]

We are hitting the ramdisk size on oxidecomputer/omicron#10847. Rust 1.97 seems to have caused a significant increase in Rust binary size:

# rust 1.96.1
iliana@atrium ~/omicron $ du -sh out/switch-asic.tar.gz
471M    out/switch-asic.tar.gz
iliana@atrium ~/omicron $ du -sh target/release/sled-agent
57.4M   target/release/sled-agent

# rust 1.97.1
iliana@atrium ~/omicron $ du -sh out/switch-asic.tar.gz
513M    out/switch-asic.tar.gz
iliana@atrium ~/omicron $ du -sh target/release/sled-agent
63.7M   target/release/sled-agent

I would like to understand the root cause at some point -- it is perhaps related to the new symbol mangling scheme -- but regardless we are going to want to update the toolchain. The above checks account for a 50 MiB (compressed) increase and I know there's many more Rust binaries in the host OS image than that, so 1200 seems safe to account for wanting to do a mass-upgrade to 1.97.1 across what we ship.

[rmustacc]

I think it really is important we understand what's going on. We can't always keep increasing in perpetuity. But I realize we don't have the cycles for that right now.