[WIP] Support polling for network congestion level

When a user is about to send a transaction or is looking at a swap
quote, we would like to inform them if the network is busy so that we can
push them to use a lower fee setting. The GasFeeController already
provides a way to poll for fee estimates, which we employ on transaction
preview screens. This commit updates the polling mechanism so that we
can also gauge the network congestion level. This is done by hitting the
`eth_feeHistory` endpoint, which was added in EIP-1559. This endpoint
allows us to see the base and priority fees that were used in the last N
blocks, where N is a number we can choose. We use this data to determine
whether there has been a recent spike in fees.

.eslintrc.js

@@ -65,6 +65,10 @@ module.exports = {
     'no-param-reassign': 'off',
     radix: 'off',
     'require-atomic-updates': 'off',
+    'jsdoc/match-description': [
+      'error',
+      { matchDescription: '^([A-Z]|[`\\d_])[\\s\\S]*[.?!`>]$' },
+    ],
   },
   settings: {
     'import/resolver': {

package.json

@@ -74,10 +74,12 @@
     "@metamask/eslint-config-jest": "^9.0.0",
     "@metamask/eslint-config-nodejs": "^9.0.0",
     "@metamask/eslint-config-typescript": "^9.0.1",
+    "@sinonjs/fake-timers": "^8.0.1",
     "@types/jest": "^26.0.22",
     "@types/node": "^14.14.31",
     "@types/punycode": "^2.1.0",
     "@types/sinon": "^9.0.10",
+    "@types/sinonjs__fake-timers": "^6.0.4",
     "@types/web3": "^1.0.6",
     "@typescript-eslint/eslint-plugin": "^4.22.0",
     "@typescript-eslint/parser": "^4.22.0",