Add test flag to override SYNC_TOLERANCE_EPOCHS for range sync testing (#7030)

Related to #6880, an issue that's usually observed on local devnets with small number of nodes.

When testing range sync, I usually shutdown a node for some period of time and restart it again. However, if it's within `SYNC_TOLERANCE_EPOCHS` (8), Lighthouse would consider the node as synced, and if it may attempt to produce a block if requested by a validator - on a local devnet, nodes frequently produce blocks - when this happens, the node ends up producing a block that would revert finality and would get disconnected from peers immediately.

### Usage

Run Lighthouse BN with this flag to override:

```
--sync-tolerance--epoch 0
```

scripts/local_testnet/network_params_das.yaml

@@ -4,11 +4,15 @@ participants:
     cl_extra_params:
       - --subscribe-all-data-column-subnets
       - --subscribe-all-subnets
+      # Note: useful for testing range sync (only produce block if node is in sync to prevent forking)
+      - --sync-tolerance-epochs=0
       - --target-peers=3
     count: 2
   - cl_type: lighthouse
     cl_image: lighthouse:local
     cl_extra_params:
+      # Note: useful for testing range sync (only produce block if node is in sync to prevent forking)
+      - --sync-tolerance-epochs=0
       - --target-peers=3
     count: 2
 network_params: