Check immutable metadata compatibility with LC

[konradkonrad]

When #7253 was merged, it claimed it "implemented part of #7242".

Since then, some e2e tests with the light client showed problems.

This issue is to investigate what the implementation status is.

[Maximilian Langenfeld]

Note #7242 (comment)
This should not be relevant for failing tests that don't have immutableMetadata=0 nodes though