[debug] Turn on --wasm-expose-debug-eval by default.

The DevTools front-end uses so-called Wasm evaluator modules to get to
the values of variables in scope when the wasmDWARFDebugging experiment
is turned on. We rely on the `Debugger.executeWasmEvaluator()` method in
the Chrome DevTools Protocol (CDP) to accomplish this, which in turn is
controlled by this global flag.

Since we intend to gather more feedback from selected internal /
external teams on the DWARF debugging experience, we need to ship this
flag by default to make it easier to test the new experiment without
having to fiddle with additional flags to pass to Chrome on the command
line (and asking folks whether they really started Chrome correctly).

Bug: chromium:1041362
Change-Id: I1e170383fa7a34c41eec8c4867c38b7d8e871e8b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2335072
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69212}

src/flags/flag-definitions.h

@@ -762,7 +762,7 @@ DEFINE_BOOL(trace_wasm_memory, false,
 DEFINE_INT(wasm_tier_mask_for_testing, 0,
            "bitmask of functions to compile with TurboFan instead of Liftoff")
 
-DEFINE_BOOL(wasm_expose_debug_eval, false,
+DEFINE_BOOL(wasm_expose_debug_eval, true,
             "Expose wasm evaluator support on the CDP")
 
 DEFINE_BOOL(validate_asm, true, "validate asm.js modules before compiling")