fixup! memory-db: allow changing the default hasher (#224)

[alexggh]

Somehow, because cargo build is using the local reference of hashdb, cargo build did not complain about:

error[E0277]: `S` cannot be shared between threads safely
   --> src/lib.rs:604:3
    |
604 |         self
    |         ^^^^ `S` cannot be shared between threads safely

But cargo publish is using the crates.io version and in that case we get the above errors, not completely sure why the local crate makes a difference, but I just fixed it.

Additionally, also set the default-features to true for foldhash, so that no_std build in polkadot-sdk works.

[michalkucharczyk]

Was this already released as memory-db 0.34.0 (likely with #224)? If yes could we have a tag please (could not found it)?

[alexggh]

Was this already released as memory-db 0.34.0 (likely with #224)? If yes could we have a tag please (could not found it)?

Sorry, forgot to push the tag it is memory-db-v0.34.0.