[debugger] Enable lldb-eval by default
[debugger] Enable lldb-eval by default

Set "lldb-eval with fallback to LLDB" as a default expression evaluation
strategy. This enables using https://github.com/google/lldb-eval as a
default engine, while still falling back to LLDB for unsupported
expressions.

This affects all built-in and custom data visualizers (NatVis) and
ad-hoc expressions via the Immediate window.

GitOrigin-RevId: 8f398f6169f86df403fd6191be69f827b2ab60d6

googlestadia/vsi-lldb,googlestadia/vsi-lldb,googlestadia/vsi-lldb