Introduce `FailoverRpcProvider` that switches between providers in case of a failure of one of them

Pre-flight checklist

[x] I have read the Contributing Guidelines on pull requests.
[x] Commit messages follow the conventional commits spec
[x] If this is a code change: I have written unit tests.
[x] If this changes code in a published package: I have run pnpm changeset to create a changeset JSON document appropriate for this change.
[ ] If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

RPC providers can experience intermittent downtime, connectivity issues, or rate limits that cause client transactions to fail. This could have been prevented if near-api-js had the FailoverRpcProvider that supports multiple RPC providers.

const jsonProviders = [
  new JsonRpcProvider({
    url: 'https://rpc.mainnet.near.org',
  }),
  new JsonRpcProvider(
    {
      url: 'https://another-rpc.cloud.com',
      headers: { 'X-Api-Key': 'some string' },
    },
    { retries: 3, backoff: 2, wait: 500 }
  ),
];
const provider = new FailoverRpcProvider(jsonProviders);

await connect({
  networkId: 'mainnet',
  provider: provider,
  // this isn't used if `provider` is specified, but is still required for backward compativility
  nodeUrl: 'https://rpc.mainnet.near.org',
});

Test Plan

Related issues/PRs

https://github.com/near/near-api-js/pull/1216 https://github.com/near/near-api-js/pull/760

Discussion https://github.com/near/near-api-js/issues/733

near / near-api-js

Introduce `FailoverRpcProvider` that switches between providers in case of a failure of one of them #1334

Pre-flight checklist

Motivation

Test Plan

Related issues/PRs

🦋 Changeset detected