test: create a WitnessConfig that removes limits (#12642)

Such config that disables limits is useful for tests/benchmarks. An
equivalent `test_disabled` already exists for `CongestionControlConfig`:


https://github.com/near/nearcore/blob/e692d204ed97add40f6fa5baea4477f9b28f9c49/core/parameters/src/config.rs#L217-L221

I plan to use `WitnessConfig::test_disabled` in a follow up PR to make
`benchmarknet` config adjustments.

core/parameters/src/config.rs

@@ -250,3 +250,16 @@ pub struct WitnessConfig {
     /// Soft size limit of storage proof used to validate new transactions in ChunkStateWitness.
     pub new_transactions_validation_state_size_soft_limit: usize,
 }
+
+impl WitnessConfig {
+    /// Creates a config that effectively disables ChunkStateWitness related limits by setting them
+    /// to max values. This can be useful for tests and benchmarks.
+    pub fn test_disabled() -> Self {
+        let max_value = usize::MAX;
+        Self {
+            main_storage_proof_size_soft_limit: max_value,
+            combined_transactions_size_limit: max_value,
+            new_transactions_validation_state_size_soft_limit: max_value,
+        }
+    }
+}