We have errors in Sentry about the log levels we send

This is because only the following levels are allowed/understood in Sentry (https://docs.sentry.io/clients/node/usage/#raven-node-additional-data):

Sentry is aware of the following levels:

• debug (the least serious)
• info
• warning
• error
• fatal (the most serious)

Expected behavior

We should send levels that Sentry understands, and map the levels we currently send as-is extracted from Java.

As we only send >= WARNING anyway, we mainly (only?) have to map severe to fatal.