Adopt ASCIILiteral in TextEncoding code instead of `const char*` to clarify the lifetime of these strings.
Pull request: https://github.com/WebKit/WebKit/pull/20636
Committed 270903@main (e59e03e1df5b): <https://commits.webkit.org/270903@main> Reviewed commits have been landed. Closing PR #20636 and removing active labels.
<rdar://problem/118571790>