Use a separate `TextPainter` for intrinsics calculation in `RenderEditable` and `RenderParagraph` (#144577)

Use a dedicated `TextPainter` for intrinsic size calculation in `RenderEditable` and `RenderParagraph`.

This is an implementation detail so the change should be covered by existing tests.  Performance wise this shouldn't be significantly slower since SkParagraph [caches the result of slower operations across different paragraphs](https://github.com/google/skia/blob/9c62e7b382cf387195ef82895530c97ccceda690/modules/skparagraph/src/ParagraphCache.cpp#L254-L272). Existing benchmarks should be able to catch potential regressions (??).

The reason for making this change is to make sure that intrinsic size computations don't destroy text layout artifacts, so I can expose the text layout as a stream of immutable `TextLayout` objects, to signify other render objects that text-layout-dependent-cache (such as caches for `getBoxesForRange` which can be relatively slow to compute) should be invalidated and  `markNeedsPaint` needs to be called if the painting logic depended on text layout.
Without this change, the intrinsics/dry layout calculations will add additional events to the text layout stream, which violates the "dry"/non-destructive contract.