remove camel case for API/Params.

[DaanHoogland]

@sureshanaparti , can we root out camel case for API/Params completely? this is techdebt byting us.

@DaanHoogland it seems camel cases (domainId, clusterId, zoneId, etc) were used in marvin tests, we can address them later in a separate pr?

Originally posted by @sureshanaparti in #12689 (comment)