fix: Blockscout and Etherscan lookups are off until the user turns them on (closes #668)

Out of the box the wallet sent the user's addresses to Blockscout and each
recipient to Etherscan. Two settings, "Use Blockscout" and "Check recipients on
Etherscan", now gate those requests. Both are off in a new install and offered
unticked on Welcome and in Settings. While one is off, the screens that relied
on it say so in a plain line. Each gated request reads its setting from storage
before it asks and when the answer lands, and drops a late answer. An open popup
takes another page's change and draws its screens again. While "Use Blockscout"
is off, no address keeps an untracked token, and no screen names a token from
Blockscout's report. ENS lookups ask only the RPC endpoint.

Model: opus-5-5 (implementation); fable-5-1 (prose)

README.md

@@ -769,8 +769,8 @@ Three limits are worth knowing, all real differences from the Chrome suite:
   The suite leaves "Use Blockscout" off, so Blockscout is not asked. A
   `ReferenceError` in the success path of `renderTransactions`, or of price
   rendering, passes this suite green. The offline run is also weaker than the
-  Chrome suite's interception: it proves nothing got out, but it cannot report
-  which requests were attempted.
+  Chrome suite's interception for those calls: it proves nothing got out, but it
+  cannot report which requests were attempted.
 - **The site-connection prompt always opens in a window of its own.** The
   profile turns off `extensions.openPopupWithoutUserGesture.enabled`, so
   `src/background/index.js` falls back from the toolbar popup, which WebDriver

src/shared/storedSettings.js

@@ -11,10 +11,9 @@
 const { storageGet } = require("./browserApi");
 const { normalizePersisted } = require("./persistedState");
 
-// Whether the setting `name` is on in the stored profile. `name` is
-// "useBlockscout" or "checkRecipientsOnEtherscan". The profile is read through
-// normalizePersisted(), as a load reads it, so only a stored true is on. A
-// failed read counts as off.
+// Whether `name`, "useBlockscout" or "checkRecipientsOnEtherscan", is on in the
+// stored profile. The profile is read through normalizePersisted(), as a load
+// reads it, so only a stored true is on. A failed read counts as off.
 async function storedSettingIsOn(name) {
     try {
         const { autistmask } = await storageGet("autistmask");