Allow configuration of guest trace storage

[dblnz]

Description

Currently, we have a fixed capacity for the Vec that stores the guest tracing events.
We want to allow the guest to configure the maximum space allowed to be allocated for the traces.

Rationale

Hyperlight does not know the guest's memory use constraints, hence allowing a guest to configure its preference at runtime, gives flexibility to the users.

How

One option would be to use a weak symbol in the guest, for which hyperlight provides a default implementation.