REST settable setting needed to set minimum Magma memory to 100MB

The current provision sets the minimum memory for a magma bucket at 1GB(MB-51292). Previously, QE requested the capability to adjust this down to 256MB for testing purposes (MB-51346) anticipating potential customer requests for lower minimums. As we continue to benchmark memory limits for magma, we would like to request permission to further reduce this quota to 100MB for additional testing.

CC: Balakumaran Gopal