* fix lib.rs and tests.rs
* update decode.rs
* auto-delete in Cargo.lock
* delete milagro in cargo.toml
* remove milagro from makefile
* remove milagro from the name
* delete milagro in comment
* delete milagro in cargo.toml
* delete in /testing/ef_tests/cargo.toml
* delete milagro in the logical OR
* delete milagro in /lighthouse/src/main.rs
* delete milagro in /crypto/bls/tests/tests.rs
* delete milagro in comment
* delete milagro in /testing//ef_test/src//cases/bls_eth_aggregate_pubkeys.rs
* delete milagro
* delete more in lib.rs
* delete more in lib.rs
* delete more in lib.rs
* delete milagro in /crypto/bls/src/lib.rs
* delete milagro in crypto/bls/src/mod.rs
* delete milagro.rs
## Issue Addressed
Closes#1264
## Proposed Changes
* Milagro BLS: tweak the feature flags so that Milagro doesn't get compiled if we're using BLST. Profiling showed that it was consuming about 1 minute of CPU time out of 60 minutes of CPU time (real time ~15 mins). A 1.6% saving.
* Reduce monomorphization: compiling for 3 different `EthSpec` types causes a heck of a lot of generic functions to be instantiated (monomorphized). Removing 2 of 3 cuts the LLVM+linking step from around 250 seconds to 180 seconds, a saving of 70 seconds (real time!). This applies only to `make` and not the CI build, because we test with the minimal spec on CI.
* Update `web3` crate to v0.13. This is perhaps the most controversial change, because it requires axing some deposit contract tools from `lcli`. I suspect these tools weren't used much anyway, and could be maintained separately, but I'm also happy to revert this change. However, it does save us a lot of compile time. With #1839, we now have 3 versions of Tokio (and all of Tokio's deps). This change brings us down to 2 versions, but 1 should be achievable once web3 (and reqwest) move to Tokio 0.3.
* Remove `lcli` from the Docker image. It's a dev tool and can be built from the repo if required.
## Issue Addressed
NA
## Proposed Changes
- Refactor the `bls` crate to support multiple BLS "backends" (e.g., milagro, blst, etc).
- Removes some duplicate, unused code in `common/rest_types/src/validator.rs`.
- Removes the old "upgrade legacy keypairs" functionality (these were unencrypted keys that haven't been supported for a few testnets, no one should be using them anymore).
## Additional Info
Most of the files changed are just inconsequential changes to function names.
## TODO
- [x] Optimization levels
- [x] Infinity point: https://github.com/supranational/blst/issues/11
- [x] Ensure milagro *and* blst are tested via CI
- [x] What to do with unsafe code?
- [x] Test infinity point in signature sets
