snapshots: automatically detect directory structure

[andy108369]

some snapshots have data and wasm directories, I think they should get automatically detected before the extraction.

they are currently getting set via these variables:

- SNAPSHOT_WASM_PATH=wasm
- SNAPSHOT_DATA_PATH=data

ref. https://github.com/ovrclk/cosmos-omnibus/issues/372

[tombeynon]

Agreed, should be easy enough to make this dynamic