feat(browser): simplify wrap/fill

[mitsuhiko]

This is a small experiment what happens if we do not define __sentry__ on our wrappers. It tries to reuse some code and removes handleEvent which is a dead code path in practice. I would prefer if i could also remove the wrap() calls on the args. As far as I can see this is all undocumented behavior and it does not look like we depend on this.

[github-actions]

size-limit report

Path	Base Size (fb87d34)	Current Size	Change
@sentry/browser - CDN Bundle (gzipped)	21.17 KB	21.14 KB	-0.14% 🔽
@sentry/browser - CDN Bundle (minified)	67.7 KB	67.44 KB	-0.38% 🔽
@sentry/browser - Webpack	22.79 KB	22.78 KB	-0.08% 🔽
@sentry/browser - Webpack - gzip = false	78.22 KB	78.11 KB	-0.15% 🔽
@sentry/react - Webpack	22.83 KB	22.81 KB	-0.08% 🔽
@sentry/nextjs Client - Webpack	47.33 KB	47.33 KB	+0.01% 🔺
@sentry/browser + @sentry/tracing - CDN Bundle (gzipped)	29.36 KB	29.34 KB	-0.08% 🔽

[mitsuhiko]

I cannot find a real world situation where the handleEvent branch is taken. There is a test for it, but it's based on a handleEvent on a function which does not appear to be a thing in reality. I believe the code might have predated the manual patching of handleEvent in the addEventHandler instrumentation. I verified that this still works.

__sentry__ itself is definitely optional and also causing issues in #4239 so taking this out seems sensible to me.