Feat: generate parameters for checkSignatures by referencing OperatorStateRetriever on-chain

[rubydusa]

Motivation:

Computation of the parameters needed for signature verification is typically done through the Eigen go or rust services. However, the rust services are not reliable at the current moment and some projects might want to have signature verifications without having to rely on these services.

This PR aims to make the computation of the NonSignerStakesAndSignature parameter easier and accessible through implementing it in OperatorStateRetriever contract

Modifications:

• added getNonSignerStakesAndSignature to OperatorStateRetriever
• added BN256G2 solidity library dependency

Result:

Computing the data necessary for performing signature verification is more accessible

[MegaRedHand]

CI's failing due to formatting: https://github.com/Layr-Labs/eigenlayer-middleware/actions/runs/14387747950/job/40347432364?pr=455

[rubydusa]

There is invalid rpc url error in the CI which I can also see happens on latest commit of dev: https://github.com/Layr-Labs/eigenlayer-middleware/actions/runs/14312178100/job/40109659601#step:5:883

However this PR has 2 failing CI checks and the latest commit in dev only has 1, so I'm not sure if these are just simply different workflows or am I missing something

[MegaRedHand]

The CI errors in this PR are due to external contributors not having access to repository secrets. I'm not sure about the failure in the latest dev commit, but it seems to be due to something similar. You can run the tests locally with:

HOLESKY_RPC_URL=<some-public-rpc> forge test -vvv
FOUNDRY_PROFILE=forktest forge test --match-contract Integration -vvv