This patch changes the code that blocks frozen chunk
modifications to no longer use triggers but to use custom
node instead. Frozen chunks is a timescaledb internal object
and should therefore not be protected by TRIGGER which is
external and creates several hazards. TRIGGERs created to
protect internal state contend with user-created triggers.
The trigger created to protect frozen chunks does not work
well with our restoring GUC which we use when restoring
logical dumps. Thirdly triggers are not functional for any
internal operations but are only working in code paths that
explicitly added trigger support.
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