Optimize the `bento.js` shared dependency bundle

[samouri]

summary
bento.js is a new binary containing dependencies which all of the bento extensions depend on (1). Things like Preact and PreactBaseElement. We should optimize this bundle to be as small as possible.

source-map-explorer

starting size: 17.62 kb brotli, 54.93 kb uncompressed
goal: < 10 kb brotli

opportunities

• (S) minimize cost of preact/compt: ~1.65
• (S) parseProps
• (S) CE Polyfill ~1.5
• (L) minimize or remove Context: ~3kb
• your idea here

cc @ampproject/wg-performance / @ampproject/wg-bento / @ampproject/wg-components

[rcebulko]

Do we need the CE polyfill on all/most browsers?

[alanorozco]

@rcebulko It's stripped out from the module build.

[alanorozco]

We can split out parse-props.js:

• {attrPrefix} is trivial (🏗 Extract {attrPrefix} and {type: 'date'} from parseProps() #36947). This shaves about 130B compressed.
• {selector}/passthrough/passthroughNonEmpty is less trivial, but would have a bigger impact (~500B) since it would extract <Slot> as well.

[alanorozco]

starting size: 17.62 kb brotli

bento.mjs is at 15.03 kb after recent changes to remove:

• CE polyfill
• side-effects from including forwardRef
• createPortal

[samouri]

Current bento.mjs is currently at 14.5 kb

[samouri]

@alanorozco / @kvchari / @jridgewell: I believe we can remove AMP Context from the CDN's bento.mjs and bento.core.module.js

[rcebulko]

AMP context may be consumed by the log system, which might still be used by bento internals. Not sure, would have to look at binaries or dependency trees