[wasm] Ship code protection via memory protection keys

Both stability and performance looks good on Linux and ChromeOS, which
is the only operation systems that currently support PKU.

Hence enable the feature by default before launching via finch.

R=ahaas@chromium.org

Bug: v8:11974, chromium:1204982
Change-Id: I2c1e7e7bb70ba73218d4db630219870b198ba6e6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3461934Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79103}

src/flags/flag-definitions.h

@@ -940,10 +940,9 @@ DEFINE_DEBUG_BOOL(trace_wasm_native_heap, false,
 DEFINE_BOOL(wasm_write_protect_code_memory, false,
             "write protect code memory on the wasm native heap with mprotect")
 DEFINE_WEAK_IMPLICATION(future, wasm_write_protect_code_memory)
-DEFINE_BOOL(wasm_memory_protection_keys, false,
-            "protect wasm code memory with PKU if available, no protection "
-            "without support; fallback to mprotect by adding "
-            "--wasm-write-protect-code-memory")
+DEFINE_BOOL(wasm_memory_protection_keys, true,
+            "protect wasm code memory with PKU if available (takes precedence "
+            "over --wasm-write-protect-code-memory)")
 DEFINE_WEAK_IMPLICATION(future, wasm_memory_protection_keys)
 DEFINE_DEBUG_BOOL(trace_wasm_serialization, false,
                   "trace serialization/deserialization")