append EL version to metrics output directory name

[jsign]

This PR adds automatic detection of the EL tag/sha of the ELs used by ere-guest/stateless-validator-{reth|ethrex}.

We had the version number for the zkVMs, but we didn't for ELs.

By doing this, we can add to the zkvm-metrics output which version of the EL was used.
Example of zkvm-metrics structure now:

zkevm-metrics
├── hardware.json
└── reth-v1.10.2
    └── zisk-v0.15.0
        ├── rpc_block_23326244.json
        ├── rpc_block_23326246.json
        ├── rpc_block_23326252.json
        ├── rpc_block_23326253.json
        └── rpc_block_23326259.json

[jsign]

@han0110, I think we could consider doing the same build.rs idea in ere-guests.

Might be useful for zkboost or other users, and even potentially appending it to the release artifacts.

If that sounds good, here I could extract it via some pub constant in ere-guests or prob just only by parsing the release artifact names.

No need to do this urgently -- but might just be another thing that we could move to ere-guest if makes sense.