Make `stateless-validator-common` no_std

[jsign]

As mentioned in the PR description, ethereum_ssz has some chain of crates dependencies which aren't no_std. Went into that rabbit hole a bit, and got pretty far but required at least these patches:

ethereum_ssz = { git = "https://github.com/han0110/ethereum_ssz", branch = "feature/no-std" }
ethereum_ssz_derive = { git = "https://github.com/han0110/ethereum_ssz", branch = "feature/no-std" }
ethereum_serde_utils = { git = "https://github.com/han0110/ethereum_serde_utils", branch = "feature/no-std" }
tree_hash = { git = "https://github.com/jsign/tree_hash", rev = "2263d501c0765837ef099796f153ba323939e614" }
tree_hash_derive = { git = "https://github.com/jsign/tree_hash", rev = "2263d501c0765837ef099796f153ba323939e614" }
ssz_types = { git = "https://github.com/jsign/ssz_types", rev = "679b7ba3e7402df8f8441af2242a6117c91fc84a" }

The first three are ones that we already did before for similar reasons, and bottom three are ones I had to do because of new needs. I got pretty close -- but there is still some extra things to do potentially. I prefered to stop and not include it in this PR since it was already quite big; but I think we can revisit this to see if we need to continue patching or there is other way.

Originally posted by @jsign in #7 (comment)