Refactored floating_ip and floating_ip_info modules

Use service proxies from openstacksdk wherever reasonable in order to
reduce calls to OpenStack API.

Renamed floating_ip_info's attribute 'project_id' to 'project' to be
consistent with other attributes and added the former as an alias to
keep backward compatibility. The latter can now also be used to search
for floating ips by project names, not only project ids.

Sorted argument specs and documentation of both modules.

Reworked integration tests, e.g. replaced references to server's
'addresses' attribute with calls to our port_info and floating_ip_info
modules. Also reformatted tests and added assertion on return values.

Merged integration tests of floating_ip_info module into floating_ip
module, because the former does not create any floating ips and
assumes that they have been created earlier.

For Zuul CI job ansible-collections-openstack-functional-devstack-\
releases to pass, the minimum required openstacksdk release must be
0.102.0 because [1],[2],[3],[4] are available since that release
only.

[1] https://review.opendev.org/c/openstack/openstacksdk/+/851976
[2] https://github.com/openstack/openstacksdk/commit/0ded7ac398843b6b1ce46668eb3b45ce02628428
[3] https://review.opendev.org/c/openstack/openstacksdk/+/859672
[4] https://github.com/openstack/openstacksdk/commit/2535ba7a28ae081f064ae20f9ddb19f48a973625

Change-Id: I129f866e7ed8d5c0499c93e78ebbe2c424e09423