Report traps and privilege level in trace

Nobody has claimed this yet.

There are a few signals in the tracer module that aren't printed to the output file:

```
// These signals are part of RVFI, but not used in this module currently.
// Keep them as part of the interface to change the tracer more easily in the future. Assigning
// these signals to unused_* signals marks them explicitly as unused, an annotation picked up by
// linters, including Verilator lint.
logic [63:0] unused_rvfi_order = rvfi_order;
logic unused_rvfi_trap = rvfi_trap;
logic unused_rvfi_halt = rvfi_halt;
logic unused_rvfi_intr = rvfi_intr;
logic [ 1:0] unused_rvfi_mode = rvfi_mode;
logic [ 1:0] unused_rvfi_ixl = rvfi_ixl;
```

It would be *really* helpful if there was an extra column for the current privilege, and for traps to be printed.

If I make a PR for this would it be accepted?

Start by locating the tracer module and its output-file format, then inspect the RVFI signals listed in the issue, especially rvfi_trap and rvfi_mode. The change is complete when trace output includes the current privilege level and trap information, with relevant tracer tests or checks updated if present.

Written by the indexing model from the issue text.