Fix #11585: Crash when cleaning AI/GS with nested AsyncMode.

Do not throw sanity check when in_shutdown is true. This is also applied to
ExecMode and TestMode as they follow the same pattern.

Change: Replace ScriptLog data array with std::deque. (#10770)

Due to cyclic header dependency this requires moving the data types used
by ScriptLog out of the ScriptLog class.

Change: Limit memory allocations for each Squirrel instance

This can avoid out-of-memory situations due to single scripts using up the entire address space.
Instead, scripts that go above the maximum are killed.
The maximum is default 1 GB per script, but can be configured by a setting.