... in DeserializeContexts.

Allocate the context before filling the scope info with the correct
variable name may cause DCHECK failure in TorqueGeneratedClassVerifiers::ScopeInfoVerify.
This CL changes the context variables serialization order from
"name, value, name, value" to "name, name... value, value...".
And only allocate and fill the context after setting up the correct
scope info.

Bug: v8:12832
Change-Id: I6e91aa867a528b7ffcae85de0f2364d0f9ea1bd7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3607374Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: 王澳 <wangao.james@bytedance.com>
Cr-Commit-Position: refs/heads/main@{#80184}