docs: Added new M samples to the Samples "What's New" page

Since I'm adding several new samples at once, I've added them
alphabetically. (Ordinarily the newest samples go at the top.)

Per our discussion, removed all the samples that used to be on the
"What's New" page.

See first comment for doc stage location.

bug: 21406143
Change-Id: Ib637ba3cf425a6b96cd97d08d5d9eefb8eac1a5d