perf(db): compact felts / bincode bad

[cchudant]

Is there an existing issue?

• I have searched the existing issues

Motivation

From @shamsasari's comment on #372:

bincode prepends a 8-byte length value, so it outputs 40 bytes instead of 32. I would suggest we use to_bytes_be directly.

Request

we use bincode a lot where we shouldn't really do it, especially for db keys.
that's a lot of wasted bytes in the db - also, in addition, for felts that are short (0x1...) we could use the 4/5 leading unused bytes to mark the length of the felt, leading to very short keys for a lot

We could also do that for values

Solution

We already tried implementing that upstream on the felt type with @jbcaron, i think, but the PR hasnt been merged: starknet-io/types-rs#76

We may want to bring it back

Are you willing to help with this request?

Maybe (please elaborate above)