Rollup merge of #84235 - klensy:styled-buffer, r=lcnr
Rollup merge of #84235 - klensy:styled-buffer, r=lcnr

refactor StyledBuffer

Refactors StyledBuffer `text` and `styles` fields content into StyledChar and touches some other stuff.

aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust