[DRAFT] move cloud snitches to external python script

[syuu1228]

This is scylla-machine-image part of "move cloud snitches to external python script" PR. Currently this PR is DRAFT version since it doesn't implemented Ec2MultiRegionSnitch yet.

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Since it's hard to debug scylla-core's cloud snitch support, we want to move them out to python script. On the python script we will generate cassandra-rackdc.properties file, and scylla-core will read it via GossipingPropertyFileSnitch code.

See scylladb/scylladb#12306

[syuu1228]

scylla-core part of the PR is at: https://github.com/scylladb/scylladb/pull/13623

[syuu1228]

I implemented JavaPropertiesParser on scylla_cloud_snitch, it's modified version of sysconfig_parser, since the format is very similar. I wanted it just for read / write cassandra-rackdc.properties, without doing regexp stuff for each read / write, since it would be hard to maintain.

But there is a pip module to parse java properties https://pypi.org/project/javaproperties/, maybe we can consider to use it.

[syuu1228]

TODO:

• Implement Ec2MultiRegionSnitch
  • find a way to configure broadcast_address, broadcast_rpc_address from the script. I think we need to modify scylla.yaml to do that
• Implement exponential backoff on curl(). Currently it just sleep 5 sec for each retries

[mykaul]

@avelanarius - hopefully, the drivers may be able to (re)use this functionality as well.