Need mechanism to evict spans from in-memory storage based on various conditions

[objectiser]

Requirement - what kind of business use case are you trying to solve?

Be able to use the in-memory storage mechanism (all-in-one image) without worrying about it running out of memory.

Problem - what in Jaeger blocks you from solving the requirement?

Currently the in-memory storage does not have any memory management mechanism - so eventually it runs out of memory and crashes.

I believe this is causing istio/istio#5782.

Proposal - what do you suggest to solve the problem or improve the existing situation?

Introduce configurable mechanism to evict spans based on max number and/or age.

Any open questions to address