v1: server_api (CXX-3237, CXX-3238)

[eramongodb]

Resolves CXX-3237 and CXX-3238 for the v1::server_api component.

mongoc_server_api_t is not used as the underlying implementatino due to the inability to convert v1::server_api::version (scoped enum: underlying type is int) to mongoc_server_api_version_t (unscoped enum: underlying type is "a suitably sized integer type"). Because "invalid API version" exceptions are only thrown upon request to convert to/from a string or by the make_server_api helper (only when required by client/pool ctors), validating this narrowing conversion with an exception would be a breaking change. Therefore, the v1::server_api fields continue to be handled independently by mongocxx rather than converted into mongoc values.

Because v1::server_api::version is completely equivalent to v_noabi::options::server_api::version, the latter is defined as an alias of the former (similar to v1::return_document). This avoids the need for v_noabi <-> v1 enumeration conversions.