set gasprice on bsctestnet (#3120)

### Description

Sets a somewhat arbitrary gas price on bsctestnet to get transactions
going for the key-funder (and presumably kathy as well). It's a pretty
blunt hammer for a not-helpful `transaction underpriced` error, but IMO
fine enough

### Drive-by changes

handleTx would not handle confirmations=0, and just set it to 1

typescript/infra/config/environments/testnet4/chains.ts

@@ -14,7 +14,12 @@ export const ethereumTestnetConfigs: ChainMap<ChainMetadata> = {
       maxPriorityFeePerGas: 40 * 10 ** 9, // 40 gwei
     },
   },
-  bsctestnet: chainMetadata.bsctestnet,
+  bsctestnet: {
+    ...chainMetadata.bsctestnet,
+    transactionOverrides: {
+      gasPrice: 80 * 10 ** 9, // 8 gwei
+    },
+  },
   goerli: chainMetadata.goerli,
   scrollsepolia: chainMetadata.scrollsepolia,
   sepolia: chainMetadata.sepolia,

typescript/sdk/src/providers/MultiProvider.ts

@@ -305,7 +305,7 @@ export class MultiProvider<MetaExt = {}> extends ChainMetadataManager<MetaExt> {
     tx: ContractTransaction | Promise<ContractTransaction>,
   ): Promise<ContractReceipt> {
     const confirmations =
-      this.getChainMetadata(chainNameOrId).blocks?.confirmations || 1;
+      this.getChainMetadata(chainNameOrId).blocks?.confirmations ?? 1;
     const response = await tx;
     const txUrl = this.tryGetExplorerTxUrl(chainNameOrId, response);
     this.logger(