[web] Reland - Switch web-render option default to auto

[ferhatb]

Description

Reland #23090

Switches web-render to default to auto detect. On desktop flutter web will start using canvas kit by default, on mobile html will be used to render. Users can still override by -web-renderer=html or canvaskit.

See public doc https://docs.google.com/document/d/1aY0iU16wf_sdT7nwfpjgT-IatHNfF3slTiYHKmxcIog/edit

After this change if you encounter issues please see https://flutter.dev/docs/development/tools/web-renderers to switch to html (prior default) or canvaskit modes explicitely.

Related Issues

flutter/flutter#72377

Tests

Covered by existing engine/framework tests.

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Breaking Change

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[nturgut]

LGTM. @yjbanov do you know if there might be any tests we forgot. I changed the following:

• web integration tests
• benchmarks
• flutter test (framework unit tests)

[yjbanov]

[yjbanov]

nit: just so it doesn't look like there's a possibility of having FLUTTER_WEB_USE_SKIA twice we could do:

'-DFLUTTER_WEB_USE_SKIA=${input.forCanvasKit}',