Add Evm Allowlist Feature to SBT Pallet

[ferrell-code]

Description

Adds evm allowlist feature. This gives a privileged account the ability to allowlist eth based addresses to mint a free zkSBT (still needs to pay for tx fee).

Minting free zkSBT requires user to generate a signature by signing the valid zkp with their eth wallet. The eth address used to sign must be on allowlist for this signature to be considered valid.

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• Connected to an issue with discussion and accepted design using zenhub "Connect issue" button below
• Added one label out of the L- group to this PR
• Added one or more labels from the A- and C- groups to this PR
• Explicitly labelled A-calamari, A-dolphin and/or A-manta if your changes are meant for/impact either of these (CI depends on it)
• Re-reviewed Files changed in the Github PR explorer.

Situational Notes:

• If adding functionality, write unit tests!
• If importing a new pallet, choose a proper module index for it, and allow it in BaseFilter. Ensure every extrinsic works from front-end. If there's corresponding tool, ensure both work for each other.
• If needed, update our Javascript/Typescript APIs. These APIs are officially used by exchanges or community developers.
• If modifying existing runtime storage items, make sure to implement storage migrations for the runtime and test them with try-runtime. This includes migrations inherited from upstream changes, and you can search the diffs for modifications of #[pallet::storage] items to check for any.

[Dengjianping]

Like ReservePrice, which can be configured onchain, but we can do it in another pr.