Port to SDK and add requests caching feature

Task list

[x] Define all streams, including primary keys, replication keys, bookmark params, and parent-chlid relationships
[x] Define pagination logic
[x] Import and map JSON schemas
[x] Create options for request caching
[x] Create initial readme
[ ] Pass built-in tests
[ ] Pass CI tests
[x] Update readme with final settings list

Requests Caching

This PR includes a new setting called requests_cache_path which reads and/or writes to an API cache directory.

This essentially gives us a capability as described here: https://gitlab.com/meltano/sdk/-/issues/30#note_863690984

MeltanoLabs / tap-gitlab