adds message signatures for epbs

[Tomi-3-0]

No description provided.

[tersec]

Run excluded_files="config.yaml|config.nims|beacon_chain.nimble"
The following files do not have an up-to-date copyright year:
- tests/test_message_signatures.nim

[Tomi-3-0]

Run excluded_files="config.yaml|config.nims|beacon_chain.nimble"
The following files do not have an up-to-date copyright year:
- tests/test_message_signatures.nim

Already did

[github-actions]

Unit Test Results

       12 files  ±  0    1 822 suites  ±0   59m 0s ⏱️ -28s
  5 350 tests +  3    5 003 ✔️ +  3  347 💤 ±0  0 ❌ ±0 
29 577 runs  +12  29 133 ✔️ +12  444 💤 ±0  0 ❌ ±0 

Results for commit 4ad721b. ± Comparison against base commit c63862c.

[shyam-patel-kira]

Hey @Tomi-3-0, can we avoid force pushing commit, now even a 1-commit change PR shows a lot of commit on my end.