Add de-dot logic to server

[simitt]

Currently Elastic agents replace restricted characters with _ for defined fields before sending the request to the APM Server; the server refuses to process the event when it contains restricted characters.
Since no agent local knowledge is required for the replacement, this could be done in the APM Server.

More concrete, agents replace *, . and " with _ for labels/tags and custom.
For transactionMarks the same characters are forbidden - check with RUM devs if they also apply a replace logic that could move to the server.