Run Extension checks conditionally

[chaudharysaket]

During the star-tup, Extension performs following checks:
Runtime check, Agent version check, Handler check, Sanity check, Vendor check. The feature, allow bypassing of Extension checks using env var NEW_RELIC_IGNORE_EXTENSION_CHECKS

• By default, all the above-mentioned start-up checks will be enabled as they help new customers onboarding smoothly.
• Environment variable NEW_RELIC_IGNORE_EXTENSION_CHECKS - a string of comma separated values:
• To disable specific checks: handler, agent, sanity, vendor
• To disable all the checks: all
• the NEW_RELIC_IGNORE_EXTENSION_CHECKS string is case insensitive