compiler: prevent recursive class glob cycles

[alixander]

Summary

• keep recursive globs out of classes and vars definition maps
• detect class-reference cycles during object and edge compilation
• return a source diagnostic instead of overflowing the Go stack

Verification

• go test ./d2ir ./d2compiler -count=1
• go test -race ./d2ir ./d2compiler -count=1
• go vet ./d2ir ./d2compiler
• the minimized issue input now compiles successfully
• full e2etests package passed
• go test ./ci/release -count=1

Fixes #2851