feat(tui): enable filtering of output in the `DebugPane`

The DebugPane currently displays both:

- internal debugger logs (e.g. state transitions), and
- program logs emitted via `TRACE_PRINT_LN`

Developers who use the debugger as a tool probably only want to see the `TRACE_PRINT_LN` related logs. Add filtering as [described in this comment](https://github.com/0xMiden/miden-debug/pull/54#discussion_r3126880909):

> have the default display of the debug window already be filtering for the `stdout` target, and provide keys to toggle the filtering

Look at the DebugPane code to understand how logs are currently displayed. The linked comment describes filtering by the 'stdout' target. Identify where logs are collected and rendered, then add a filter to show only TRACE_PRINT_LN logs by default and implement key bindings to toggle this filter. Check for existing key handling in the TUI to integrate the toggle.

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