Intercept shall use SQLight instead of memory for the received events

[rizsotto]

Currently the process lifetime events are arriving to intercept via gRPC and those events gets processed and stored in the memory. This hurts when compiling big projects.

• intercept shall just append all received events into an SQLight database file.
• citnames can read that file to create the JSON compilation database.

Event table can have:

• event id, unique id generated when the event received.
• reporter id (is in the message), unique id of the reporter. (all events belongs to the same process will share this id. was introduced when the PID were not unique enough.)
• timestamp (is in the message), when the message was created
• event itself (as a JSON field)

[rizsotto]

The intercept command has nearly constant memory allocation. (Allocation fragmentation is still there, but the new memory allocation rate is significantly less.) Here are the before and after pictures

The citnames command still reads all command into memory before it starts the filtering, but the allocation is still smaller than the old version. It got significantly slower 15s from 1s in my measurement. That could be a subject to improve.

[rizsotto]

contributes to #350