fix(core): Suppress stack when SentryError isn't an error

[lobsterkatie]

We use SentryErrors in our event processing and sending pipeline both when something has gone legitimately wrong and when we just want to bail on a promise chain. In all cases, however, we log both the message and the stack, at a warning log level, which both clutters the logs and unnecessarily alarms anyone who has logging on.

This fixes that by adding a logLevel property to the SentryError class, which can be read before we log to the console. The default behavior remains the same (log the full error, using logger.warn), but now we have the option of passing 'log' as a second constructor parameter, in order to mark a given SentryError as something which should only be logger.logged and whose stack should be suppressed.

(To answer the inevitable Why now? question, it's because it was making my test app logs really hard to read and it finally drove me one banana too far.)

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.4 KB (+0.09% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	60.06 KB (+0.11% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	17.97 KB (+0.08% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	52.92 KB (+0.1% 🔺)
@sentry/browser - Webpack (gzipped + minified)	19.77 KB (+0.2% 🔺)
@sentry/browser - Webpack (minified)	64.3 KB (+0.15% 🔺)
@sentry/react - Webpack (gzipped + minified)	19.79 KB (+0.19% 🔺)
@sentry/nextjs Client - Webpack (gzipped + minified)	44.43 KB (+0.1% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	25.9 KB (+0.06% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.28 KB (+0.07% 🔺)