Spin 4.0

[itowlson]

Work in progress! I've put the initial "fork all the things" stuff in the initial commit so in principle you can review the boilerplate for boilerplatey things and the content changes for actual content separately, but I dunno, maybe I should make two separate PRs, anyway, v4, WIP.

File	Changes	Status
api-guides-overview.md	Noted asyncness - need to confirm which APIs we are asyncifying
build.md	Build profiles - added	Completed
cache.md	None	Completed
cli-reference.md	Regenerate when Spin 4 stabilises	Pending
contributing-docs.md	None	Completed
contributing-spin.md	None	Completed
deploying.md	Remove Fermyon Cloud	Completed
distributing-apps.md	Build profiles - added	Completed
dynamic-configuration.md	None	Completed
extending-and-embedding.md	None	Completed
go-components.md
http-outbound.md
http-trigger.md	Instance reuse - added. http_service - added.	Started
index.md	None	Completed
install.md	None	Completed
javascript-components.md
kv-store-api-guide.md
language-support-overview.md
managing-plugins.md	None	Completed
managing-templates.md	None	Completed
manifest-reference.md	Build profiles - added	Completed
mqtt-outbound.md
observing-apps.md
other-languages.md
plugin-authoring.md	None	Completed
python-components.md
quickstart.md
rdbms-storage.md
redis-outbound.md
redis-trigger.md
running-apps.md
rust-components.md
see-what-people-have-built-with-spin.md	None	Completed
serverless-ai-api-guide.md
spin-application-structure.md	Changed http_component to http_service. Revisit once template and response body stuff is sorted.
sqlite-api-guide.md
template-authoring.md	None	Completed
testing-apps.md
triggers.md
troubleshooting-application-dev.md
upgrade.md	None	Completed
variables.md	Async, http_service, response guff	Started
writing-apps.md

General things:

• Updated remaining wasm32-wasip1 to wasm32-wasip2