rust-compress-state debug: indent the chonky json

[pushytoxin]

If the room list gets posted in the debug step, at least make it readable.

However something doesn't seem right to me.
Internally, {{ matrix_synapse_rust_synapse_compress_state_eligible_rooms }} is an array of objects, not a JSON string.
The debug step should have a sane default to pretty print the output, and not rely on us manually applying the filter.
If there is a way to configure what filter is used when Ansible is printing data to a terminal, let me know please.

[pushytoxin]

Upon closer inspection, the the data that is printed by default isn't actually JSON

[{''room_id'': ''!iyIlasdfasdfRmRHFx:matrix.org'', ''count'': 8621734},
{''room_id'': ''!Oasdfasdfasdfasdfm:matrix.org'', ''count'': 6077025}...
]

Indentation is mine, but the '' isn't.
This is too weird for me. I'm signing off this PR.

[spantaleev]

So.. does this PR make things better or not? |to_yaml may be another possibility.

If we can make it more readable, that'd nice, but it's not too important. It's a debug step, after all ;) Mostly to help us (or the user) debug things, should they go wrong.

[pushytoxin]

The message is informative, I think it's nice to have, it's just not very readable by default. Either YAML or JSON should work equally well.