fix(coprocessor): add missing indices for ciphertext_digest table (#1450)

* `idx_ciphertext_digest_handle` - we want the txn-sender to select by
   handle only
 * `idx_ciphertext_digest_unsent` - we want the txn-sender to
   select unsent txns with ordered limited retries efficiently

Furthermore, add fair ordering of rows in the ciphertext_digest table by
tracking when entries are created and order by that in the txn-sender.

Also, update the `svm-rs-builds` dependency to fix an issue with it
failing to fetch 0.8.31 prerelease version during build time from the
Soliditylang JSON file.

Author: dartdart26

coprocessor/fhevm-engine/.sqlx/query-a74057b8122baa26cff2f59a9e0e7403bb1abe1881fd3da8757e192da9f84180.json renamed to coprocessor/fhevm-engine/.sqlx/query-77a440566615702c5cec52195809b5c1e27c3b50bda491f62cd9455c07a582aa.json

@@ -0,0 +1,11 @@
+-- Track when entries are created for fair queuing of unsent transactions.
+ALTER TABLE ciphertext_digest
+ADD COLUMN IF NOT EXISTS created_at TIMESTAMP NOT NULL DEFAULT NOW();
+
+-- Handle SELECTs on handle only by the txn-sender.
+CREATE INDEX IF NOT EXISTS idx_ciphertext_digest_handle
+ON ciphertext_digest (handle);
+
+-- Handle SELECTs on unsent txns with limited retries by the txn-sender.
+CREATE INDEX IF NOT EXISTS idx_ciphertext_digest_unsent
+ON ciphertext_digest (txn_is_sent, created_at);

coprocessor/fhevm-engine/.sqlx/query-fd37e7dc679caa21ba22d7724a27409c232cceb719aa41a71e7faf44d2cb8ef9.json

@@ -310,6 +310,7 @@ where
             AND ciphertext IS NOT NULL
             AND ciphertext128 IS NOT NULL
             AND txn_limited_retries_count < $1
+            ORDER BY created_at ASC
             LIMIT $2",
             self.conf.add_ciphertexts_max_retries,
             self.conf.add_ciphertexts_batch_limit as i64,