d3d11: restore D3D11 feature-level 9.x fallback (re-enable DX9-class support)

[leonardoxr]

Motivation

• Re-enable DX9-class device initialization paths by restoring D3D11 feature-level fallbacks that were removed, so older hardware can initialize via the D3D11 backend.

Description

• Updated src/renderer_d3d11.cpp to include D3D_FEATURE_LEVEL_9_3, D3D_FEATURE_LEVEL_9_2, and D3D_FEATURE_LEVEL_9_1 in the feature-level list passed to D3D11CreateDevice on Windows builds, removing the previous BX_PLATFORM_WINRT gating and ensuring 9.x fallbacks are always considered.
• No other renderer logic was modified; existing FL9.x handling (caps/limits/conditionals) is left intact and will be used when a 9.x feature-level device is created.

Testing

• Verified the inserted feature levels are present with rg -n "D3D_FEATURE_LEVEL_9_3|D3D_FEATURE_LEVEL_9_2|D3D_FEATURE_LEVEL_9_1" src/renderer_d3d11.cpp, which succeeded.
• Confirmed the patch was applied and produced the expected diff with git diff -- src/renderer_d3d11.cpp, which showed the updated feature-level array.
• Attempted to fetch upstream metadata (git fetch upstream) for cross-reference, but the network request failed with a 403 due to environment network restrictions, so external upstream verification was not completed.

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Codex Task