Fixes #107467.

See the issue for details on the problem that is being fixed.

With this change in place, the repro app discussed in the issue runs indefinitely without ever failing (in the same environment where, without this change, the repro app always gets stuck in an infinite loop within the first several minutes of execution). This observed behavior is consistent across Checked and Release builds of the rutime.

Note that the new lock acquire statement in StandardSegmentIterator is identical to the ones which already run in FullSegmentIterator under certain conditions.

The new code only translates to a new lock acquire during any Gen1-or-larger foreground GCs which specifically occur in an environment where preceding handle table activity in the process has driven "whole-block" allocs/frees and has therefore forced "fResortChains" back to true.

I believe that the handle table lock is generally lightly contended while foreground GC is in progress. So even in scenarios which manage to chronically drive "whole-block" allocs/frees in the steady state (and thus push the new lock acquire to the worst-case "one per handle table per Gen1-or-larger foreground GC" rate), I believe that the cost of the new lock acquire will generally be negligible.

(Other than adding a new lock acquire, I believe the only other option for fixing this problem would be to somehow rework the system to eliminate and ban any notion that handle table slots can be created or destroyed by the coreclr!Thread ctor or any other preemptive-mode code.)