[wk-libs] make network-snapshots for tests readable & idempotent

[jstriebel]

Description:

Makes the network-snapshots for tests idempotent and more readable. There's still the exception of webknossos/tests/cassettes/test_examples/test_user_times.yaml which would currently yield user-data and is mostly left as-is for now.

The responses and requests are now adapted, so that

• zips are unpacked
• timestamps are filtered
• tokens are filtered
• lastUsedByUser is filtered
• loggedTime is filtered to years <= 2021
• resumable upload UUIDs are filtered
• varying metadata content-type: multipart/form-data; boundary=… is filtered

Issues:

• part of improve wk-lib snapshot tests #514

[fm3]

LGTM, please add some explaining high-level comments, especially for methods where the name was fixed and is not very descriptive. Looking forward to this change :) (and the next one with the isolated wk instance :D)