validator/twitter: Switch to guest OAuth + official API method

[nykma]

Too much pain implementing this:

• [x] Acquire OAuth token
• [x] (lambda): Reuse existed OAuth token, rotation mechanism
• [ ] Use Official API to query tweets

[nykma]

Posponed.

Seems like Twitter / X is blacklisting common VPS' IP range to prevent us from getting a valid guest token.

Further discussion: zedeus/nitter issues/983 (just don't want to mention and bother them)