engine/metamorphic: Run MVCC metamorphic tests with varying pebble/rocksdb options

[itsbilal]

Currently, the MVCC metamorphic tests start Pebble and RocksDB engines with the same default set of options. Rotating between multiple sets of options, for example to encourage smaller and larger SSTables as well as to populate more levels of the LSM tree would probably yield more interesting results.

The Pebble metamorphic test suite currently runs all operations with default options, a couple standard option sets, and some randomized options.

[itsbilal]

Merged in #46057