This is a reland of b06f3832

s/DEFINE_READONLY_BOOL/DEFINE_BOOL_READONLY/

Original change's description:
> [flag] Disable W^X behind --future
>
> Measure the impact of W^X on --future bots
>
> Change-Id: I6f60cc835471fa62ec0871101eca5d3022ece519
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3168277
> Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> Auto-Submit: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#76908}

Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_dbg_ng,v8_mac_arm64_compile_dbg
Change-Id: Iae6da3a64d19d3c03d565cc94f765bc41e36bfb1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3168620
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76916}