[wasm][memory64] Implement 64-bit init expressions

For memory64, the init expressions for data segments provide a 64-bit
value. This CL adds a new {EvalUint64InitExpr} function alongside
{EvalUint32InitExpr}. It supports i64.const and global.get operations.

R=manoskouk@chromium.org

Bug: v8:10949
Change-Id: I58acbb28acb8771a0947f9d5df1c14e6ca0f79cf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2632589


Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72131}