Enable BLS portable feature on all CI tests (#4868)

## Issue Addressed

Addresses the recent CI failures caused by caching `blst` for the wrong CPU type. 

## Proposed Changes

- Use `FEATURES: jemalloc,portable` when building Lighthouse & `lcli` in tests
- Add a new `TEST_FEATURES` and set to `portable` for all CI test jobs.
- Updated Makefiles to read the `TEST_FEATURES` environment variable, and default to none.

consensus/state_processing/Cargo.toml

@@ -40,3 +40,4 @@ arbitrary-fuzz = [
   "ssz_types/arbitrary",
   "tree_hash/arbitrary",
 ]
+portable = ["bls/supranational-portable"]