L2: Forbid panics

[ilitteri]

Add the following clippy lint to all Cargo.toml files in the l2 crate:

[lints.clippy]
panic = "deny"

and remove the panics of the module if necessary.

[varun-doshi]

I can take this up.
To clarify, this would make panic throw compile time errors so that we'd have to return a proper error.
I see some functions do not have a return type. Should I add a return type of Result<(),Error> there?