Write OpenFX plug-in for FileTransform

Issue #1117 requests OpenFX plug-ins for OCIO and Michael has PR #1371 in progress that is almost complete to implement a ColorSpaceTransform and DisplayViewTransform plug-in, which are the key ones. It would also be great to have a few more OpenFX plug-ins, for example for FileTransform. This would allow people to apply stand-alone LUTs in any of the formats OCIO supports, including the Academy/ASC Common LUT Format (CLF). The implementation should include an "invert" toggle button, similar to Michael's work.

It would also be great to have OpenFX plug-ins for LookTransform and NamedTransform, although these could also be in separate PRs.

从 issue #1117 和 PR #1371 开始，它们提供了 OpenColorIO 现有 OpenFX 插件的背景。确定 FileTransform 插件应如何与 ColorSpaceTransform 和 DisplayViewTransform 的工作配合，包括 invert 切换开关。完成的标准是，FileTransform OpenFX 插件可以应用受支持的独立 LUT 格式，包括 CLF；LookTransform 和 NamedTransform 属于单独的后续范围。

由索引模型根据 Issue 内容生成。