[Meta] Async/await conversion of auth server routes and libs

[jaredhirsch]

Copying over the list of routes from #2286. Add your name next to a checkbox item if you start refactoring it.

• account.js @chenba, refactor(api): prefer async/await in lib/routes/account.js #3655
• attached-clients.js (already using async/await)
• defaults.js @shane-tomlinson
• devices-and-sessions.js @philbooth, refactor(api): prefer async/await in device/session routes #2301
• emails.js @chenba refactor(api): prefer async/await in emails routes #2324
• idp.js (made no promises)
• index.js (made no promises)
• oauth.js (already using async/await)
• password.js @6a68 working on this one
• recovery-codes.js @philbooth, refactor(api): prefer async/await in recovery-codes routes #2387
• recovery-key.js @philbooth, refactor(api): prefer async/await in recovery-key routes #2386
• security-events.js (already using async/await)
• session.js @philbooth, refactor(api): prefer async/await in session routes #2384
• sign.js @dannycoates
• signin-codes.js @philbooth, refactor(api): prefer async/await in signin-codes route #2383
• sms.js @philbooth, refactor(api): prefer async/await in sms routes #2382
• subscriptions.js (already using async/await)
• support.js (already using async/await)
• token-codes.js @philbooth, refactor(api): prefer async/await in token codes routes #2381
• totp.js
• unblock-codes.js PR refactor(unblock-codes): Convert unblock-codes.js to async/await  #2292
• util.js
• utils/clients.js (made no promises)
• utils/email.js (made no promises)
• utils/oauth.js (already using async/await)
• utils/request_helper.js (made no promises)
• utils/signin.js shane-tomlinson
• utils/signup.js (@bbangert)
• utils/subscriptions.js (already using async/await)
• utils/otp.js (@bbangert)
• validators.js (made no promises)

Some non-routes libs that we can also investigate and convert:

(Note, the number at the end is the number of instances of .then in the file)

• metrics/amplitude.js (3) (@shane-tomlinson)
• metrics/events.js (8) (@shane-tomlinson)
• metrics/context.js (3) (@bbangert)
• crypto/random.js (3)
• crypto/password.js (5)
• scheme-refresh-token.js (5) (@bbangert)
• customs.js (5) (@bbangert)
• subhub/client.js (1)
• features.js (1)
• cache.js (4) (@bbangert)
• server.js (6) (@bbangert)
• db.js (51) (@bbangert)
• pushbox.js (2)
• backendService.js (2)
• oauthdb/index.js (1)
• oauthdb/utils.js (3)
• log.js (1)
• error.js (5) (no promises, just "authentication")
• senders/index.js (2) (no promises, just "authentication")
• senders/translator.js (2) @lmorchard, refactor(auth-server): prefer async/await in lib/senders/translator.js #2421
• senders/sms.js (5)
• senders/email.js (15)
• signer.js (3) (@bbangert)
• profile/updates.js (2) (@bbangert)
• push.js (4) (@bbangert)
• devices.js (4) (@bbangert)
• authMethods.js (11) (@bbangert)
• tokens/bundle.js (4) (@bbangert)
• tokens/password_forgot_token.js (1) (@bbangert)
• tokens/key_fetch_token.js (3) (@bbangert)
• tokens/token.js (6) (@bbangert)
• tokens/session_token.js (5) (@bbangert)
• email/bounces.js (6) (@bbangert)
• email/delivery.js (1) (@bbangert)

┆Issue is synchronized with this Jira Epic
┆Issue Number: FXA-297

[clouserw]

epics are tracked in jira