feat(tee): use hex deserialization for RPC requests

Following Anton's suggestion, we have switched to hex serialization for
API/RPC requests and responses. Previously, we used default JSON
serialization for Vec<u8>, which resulted in a lengthy comma-separated
list of integers.

This change standardizes serialization, making it more efficient and
reducing the size of the responses. The previous format, with a series
of comma-separated integers for pubkey-like fields, looked odd.

Then:
```
curl -X POST\
     -H "Content-Type: application/json" \
     --data '{"jsonrpc": "2.0", "id": 1, "method": "unstable_getTeeProofs", "params": [491882, "Sgx"] }' \
        https://mainnet.era.zksync.io
{"jsonrpc":"2.0","result":[{"attestation":[3,0,2,0,0,0,0,0,10,<dozens of comma-separated integers here>
```

Now:
```
$ curl -X POST \
       -H "Content-Type: application/json" \
       --data '{"jsonrpc": "2.0", "id": 1, "method": "unstable_getTeeProofs", "params": [1, "sgx"] }' \
          http://localhost:3050
{"jsonrpc":"2.0","result":[{"l1BatchNumber":1,"teeType":"sgx","pubkey":"0506070809","signature":"0001020304","proof":"0a0b0c0d0e","provedAt":"2024-09-16T11:53:38.253033Z","attestation":"0403020100"}],"id":1}
```

This change needs to be deployed in lockstep with:
https://github.com/matter-labs/zksync-era/pull/2887.

Cargo.lock

@@ -5636,6 +5636,7 @@ dependencies = [
  "reqwest 0.12.7",
  "secp256k1 0.29.1",
  "serde",
+ "serde_with 3.9.0",
  "teepot",
  "tokio",
  "tracing",