feat: Refactor request logic

[benjackwhite]

Changes

Our code paths around making api requests is messy to say the least. Makes it hard to reason on, hard to make changes and includes a lot of spaghetti code that inflates the bundle size.

• Simplify everything down to a single request function that handles choosing the right available transport.
• Refactored a bunch of nested inherited types that meant it was super unclear what was going on
• Simplified compression greatly - only request needs to know about the internals of it now
• Makes base64 compression the default for capture calls (this was implicitly the default before - now it is explicit)
• Make retriable and non-retriable requests explicit
• Add timeouts

This is a pretty huge PR 😬 - not much to be done about it other than say - sorry! Focused on making sure all tests pass but there is a lot of spaghetti logic before that was unpicked hence the big diff.

Checklist

• Tests for new code (see advice on the tests we use)
• Accounted for the impact of any changes across different browsers
• Accounted for backwards compatibility of any changes (no breaking changes in posthog-js!)

[github-actions]

Size Change: -13.5 kB (-2%)

Total Size: 849 kB

Filename	Size	Change
dist/array.full.js	182 kB	-3.55 kB (-2%)
dist/array.js	123 kB	-3.53 kB (-3%)
dist/es.js	123 kB	-3.47 kB (-3%)
dist/exception-autocapture.js	12.1 kB	+73 B (+1%)
dist/module.js	123 kB	-3.4 kB (-3%)
dist/recorder-v2.js	106 kB	+67 B (0%)
dist/recorder.js	58.7 kB	+91 B (0%)
dist/surveys-module-previews.js	62.1 kB	+87 B (0%)
dist/surveys.js	58.4 kB	+87 B (0%)

_{compressed-size-action}

[benjackwhite]

This never made sense as different requests require different methods

[neilkakkar]

Ran locally, all seems to work 👍 - great job!