build: add production/development export conditions

[danielroe]

In Nitro, we create a minimal node_modules/ just for our final output. This traces the files that are used, respecting the correct export conditions.

At the moment, NODE_ENV governs whether we load the prod/dev CJS versions of the Vue packages. However, we can support custom export conditions like production and development (see nodejs reference). These have broad community support and can be used on the CLI (for example, with node --conditions=development index.js) and by bundlers like Nitro which have support for them.

This PR adds production/development conditions for the Node/CJS bundles. To make it backwards compatible it:

1. adds ./* as a subpath export so any file that was previously fully specified can continue to be fully specified (e.g. @vue/compiler-core/package.json
2. Adds a default condition that falls back the previous behaviour (e.g. if no production/development condition is explicitly specified)

I've tested this with Nuxt (see repo and Stackblitz). It enables us to reduce the output bundle by 1.2Mb.

Related unjs/nitro#2046

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	89.4 kB	34 kB	30.7 kB
vue.global.prod.js	146 kB	53.3 kB	47.5 kB

Usages

Name	Size	Gzip	Brotli
createApp	49.8 kB	19.5 kB	17.8 kB
createSSRApp	53.1 kB	20.8 kB	19 kB
defineCustomElement	52 kB	20.2 kB	18.5 kB
overall	63.2 kB	24.4 kB	22.2 kB

[yyx990803]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
language-tools	❌ failure	❌ failure
nuxt	✅ success	✅ success
pinia	✅ success	✅ success
quasar	✅ success	✅ success
router	✅ success	✅ success
test-utils	✅ success	✅ success
vant	✅ success	✅ success
vite-plugin-vue	✅ success	✅ success
vitepress	✅ success	✅ success
vue-i18n	✅ success	✅ success
vue-macros	❌ failure	❌ failure
vuetify	❌ failure	❌ failure
vueuse	✅ success	✅ success
vue-simple-compiler	✅ success	✅ success