Update metric normalization

[cleptric]

https://develop-git-statsd-unicode-escapes.sentry.dev/sdk/metrics/#normalization

closes #1731

[cleptric]

@stayallive When you look at the linked docs, regarding Line Feed, Carriage Return and Tab.
I don't think you can use these characters in PHP. Or can you?

[stayallive]

You can right... "\n\r\t" (only inside ")?

So technically you can, but it's a stretch anyone would do it on purpose. But should also be easy to replace right? Something like str_replace(["\n", "\r", ...], ['\n', '\r', ...], $item) I'm thinking?

[stayallive]

Code wise this looks good!