Add stack depth check to all Task continuations (dotnet/coreclr#23152)

Add stack depth check to all Task continuations (dotnet/coreclr#23152)

Currently Task has a stack depth check that avoids stack overflows on very deep stack continuation chains, but it only applies to Task.ContinueWith, not to other kinds of continuations.  This changes that to have it apply to all.

As part of this, this also deletes the current StackGuard type used to achieve the check.  The type was meant to avoid expensive calls to check where we are on the stack, but now that we're using TryEnsureSufficientExecutionStack, it's actually faster to just call that rather than access the current StackGuard from a ThreadLocal.  This then also cleans up the call sites nicely, as they no longer need finally blocks to undo the increment performed on the StackGuard.

Commit migrated from https://github.com/dotnet/coreclr/commit/6633b51df7f91623190ba6bf04c00869cd0fc1e4