use esbuild native watch mode for unminified builds (#32879)
use esbuild native watch mode for unminified builds (#32879)

* build-system: Use native esbuild watch mode with incremental.

* Revert "build-system: Use native esbuild watch mode with incremental."

This reverts commit ca7199a1b58f337c62e5f9beebf591436e6a02cb.

* Less intrusive change: dont use native watch.

* raghu feedback

* more raghu comment

* eek. sorry about this diff

* move finishBundle to .then(), logLevel silent
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