[LLDB][ARM] Extend testing for vpush emulation

https://reviews.llvm.org/D131658 found a bug in
ReadPseudoRegisterValue which would mean we read out
of bounds if the s register number was high enough.

This adds a memory check to vpush-1-thumb, which
should have been doing that anyway. Then copies that
test and uses the last 4 s registers instead.

Without the mentioned fix we see random values in
the final memory, with the fix it passes.

Reviewed By: fixathon

Differential Revision: https://reviews.llvm.org/D131663