refactor: move the calldata decoder to src/shared/calldataDecoder.js (closes #759)

decodeCalldata() and tokenAmountText() move out of the TxApproval view into
src/shared/calldataDecoder.js. TxApproval, TransactionDetail and the decoder
tests import them from there.

tokenSourcesByChainId() moves from the popup view helpers to
src/shared/state.js, beside currentNetwork(), so the decoder requires nothing
under src/popup/. It reads only the state singleton and the network table.

Model: opus-5-5

src/popup/views/helpers.js

@@ -31,7 +31,12 @@ const { escapeHtml } = require("../../shared/html");
 const { isDebug } = require("../../shared/log");
 const { networkByChainId } = require("../../shared/networks");
 const { formatUsd, getPrice } = require("../../shared/prices");
-const { state, saveState, currentNetwork } = require("../../shared/state");
+const {
+    state,
+    saveState,
+    currentNetwork,
+    tokenSourcesByChainId,
+} = require("../../shared/state");
 const { displaySymbol } = require("../../shared/symbolDisplay");
 const { isSpoofedSymbol } = require("../../shared/symbolSpoof");
 const { walletHasRecoveryPhrase } = require("../../shared/wallet");
@@ -305,32 +310,6 @@ function nativeCurrency() {
     return currentNetwork().nativeCurrency;
 }
 
-// What the wallet knows of the tokens on the network with this chain id, or
-// on the active network when no chain id is given, as the `sources` that
-// resolveTokenSymbol() and resolveTokenDecimals() take. A contract address
-// names a token on one network only, and every token balance held is the
-// active network's, so another network gets the tokens tracked on it
-// (state.networkTrackedTokens, see applyChainSwitchFields()) and no balances.
-//
-// The wallets' balances hold what Blockscout reported for each token. So the
-// wallets are returned only while "Use Blockscout" is on.
-function tokenSourcesByChainId(chainId) {
-    const chainIdOrActive = chainId || currentNetwork().chainId;
-    const net = networkByChainId(chainIdOrActive);
-    if (net && net.id === state.networkId) {
-        return {
-            chainId: chainIdOrActive,
-            trackedTokens: state.trackedTokens,
-            wallets: state.useBlockscout ? state.wallets : [],
-        };
-    }
-    return {
-        chainId: chainIdOrActive,
-        trackedTokens: (net && state.networkTrackedTokens[net.id]) || [],
-        wallets: [],
-    };
-}
-
 // The line shown under a token while "Use Blockscout" is off. The token gets
 // the line only when the bundled list and the tracked tokens lack its name or
 // decimals. Otherwise this returns "". The token is a contract address on the
@@ -866,7 +845,6 @@ module.exports = {
     keyMaterialName,
     unknownableAmount,
     nativeCurrency,
-    tokenSourcesByChainId,
     blockscoutOffTokenNoteHtml,
     tokenLabel,
     formatFee,