Fix production JS builds compiling JSX in development mode

[Naragod]

Cherry-picks #8150 onto release so the branch builds a correct production bundle on its own.

Why

v2.10.2 shipped without this fix. @babel/preset-react compiled JSX in development mode, so the production bundle called jsxDEV, which React's production build does not provide. The bundle died on its first component and pages lost their React tables.

The workaround on the servers was an asset rebuild with NODE_ENV=production exported by hand. This commit makes the build set it itself.

Scope

File	Change
babel.config.js	preset-react receives development: isDevelopmentEnv || isTestEnv
webpack.production.js	sets BABEL_ENV and NODE_ENV before webpack loads
Changelog.md	one bug-fix line under [unreleased]

Verification

• Clean cherry-pick of ec4bf2b from master. Zero conflicts.
• babel.config.js and webpack.production.js md5-match master byte for byte.
• Both files also md5-match the copies running on ben and tiny, where the rebuilt bundle carries zero jsxDEV calls.
• Original PR Fix production JS builds compiling JSX in development mode #8150 passed jest, rspec, brakeman, CodeQL, and pre-commit on master.

Tag

The v2.10.2 tag stays where it is. This commit lands on release only, so deployed boxes stop being a hand patch. #8150 keeps its v2.10.3 milestone.

[david-yz-liu]

Looks good to me, thanks @Naragod

[coveralls]

Coverage Report for CI Build 34390073319

Warning

No base build found for commit 8b3a14a on release.
Coverage changes can't be calculated without a base build.
If a base build is processing, this comment will update automatically when it completes.

Coverage: 90.514%

Details

• Patch coverage: No coverable lines changed in this PR.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

Requires a base build to compare against. How to fix this →

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Coverage Stats

Relevant Lines:	51662
Covered Lines:	47781
Line Coverage:	92.49%
Relevant Branches:	2471
Covered Branches:	1217
Branch Coverage:	49.25%
Branches in Coverage %:	Yes
Coverage Strength:	133.89 hits per line

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💛 - Coveralls