ref(utils): Simplify normalization code and be more specific when erroring

[lobsterkatie]

Currently, if an error occurs anywhere in the normalization process, the entire value is clobbered, in favor of the string "**non-serializable**". This has a few drawbacks:

• All data is lost, even data that wasn't malformed
• It's harder to tell where the problem is, because there's no way to know which part of the data caused the problem
• It's possible to pass normalize an object and get back a string, which can prove problematic if data is later added to the normalized property as if it were still an object (see the issue linked below).

The goal of this PR, then, was to identify all of the places where errors could occur and catch them right there, rather than relying on the try-catch in the main normalize function. In order to make this easier to reason about, the normalization code was first streamlined a bit. Key changes:

• serializeValue and makeSerializable have been combined into a single function, stringifyValue, and any code not resulting in a string has been moved into the calling function.
• All code in stringifyValue has been wrapped in a try-catch, so that errors which originate there will only affect the value at hand, rather than then entire object.
• When "**non-serializable**" has to be used, it's now accompanied by the message belonging to the error which broke the serialization.
• When the outer normalize function needs to return "**non-serializable**", it now wraps it in an object, so that other data can still be added.
• The walk function has been renamed visit, to better conform to the language of the Visitor Pattern. For the moment, it's still aliased to walk when exported, to preserve backwards compatibility.
• The getWalkSource function has been renamed convertToPlainObject, to better reflect what it does, and some of its repetitive code has been extracted into the serializeEventTarget and getOwnProperties functions.

Fixes #4719

Ref: https://getsentry.atlassian.net/browse/WEB-703

[github-actions]

size-limit report

Path	Base Size (437d7cd)	Current Size	Change
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.58 KB	19.62 KB	+0.18% 🔺
@sentry/browser - ES5 CDN Bundle (minified)	62.46 KB	62.43 KB	-0.06% 🔽
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.19 KB	18.28 KB	+0.49% 🔺
@sentry/browser - ES6 CDN Bundle (minified)	55.96 KB	55.94 KB	-0.03% 🔽
@sentry/browser - Webpack (gzipped + minified)	22.72 KB	22.77 KB	+0.21% 🔺
@sentry/browser - Webpack (minified)	80.38 KB	80.4 KB	+0.03% 🔺
@sentry/react - Webpack (gzipped + minified)	22.76 KB	22.81 KB	+0.22% 🔺
@sentry/nextjs Client - Webpack (gzipped + minified)	47.69 KB	47.75 KB	+0.12% 🔺
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	25.46 KB	25.49 KB	+0.15% 🔺
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	23.81 KB	23.88 KB	+0.31% 🔺

[AbhiPrasad]

cc @timfish

[lforst]

This is a great PR. It simplifies a lot! I left some thoughts (and maybe a bug?) below.

[timfish]

Looks like @lforst has already give this a comprehensive review but looks like a good improvement!

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.64 KB (+0.17% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	62.7 KB (-0.09% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.31 KB (+0.55% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	56.22 KB (-0.06% 🔽)
@sentry/browser - Webpack (gzipped + minified)	22.8 KB (+0.29% 🔺)
@sentry/browser - Webpack (minified)	80.69 KB (+0.02% 🔺)
@sentry/react - Webpack (gzipped + minified)	22.84 KB (+0.3% 🔺)
@sentry/nextjs Client - Webpack (gzipped + minified)	47.77 KB (+0.14% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	25.52 KB (+0.14% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	23.92 KB (+0.37% 🔺)