By Niket Nishant and Aditya Soni (Reuters) -Alphabet (GOOG) shares rallied nearly 6% to a record high on Monday after Berkshire Hathaway's (BRK-B) new stake provided an endorsement of the tech giant's artificial intelligence efforts amid heightened worries over a looming bubble. The purchase of 17.​85 million Alphabet shares - worth about $4.93 billion as of close on Friday - is one of the final major investments by ‌the conglomerate under Warren Buffett and marks a rare foray into the industry by tech-a ...