LLDB doesn't pass through language options to `ide::isSourceInputComplete`

[hamishknight]

When checking for the end of the line in the REPL, LLDB calls into the compiler's ide::isSourceInputComplete, but doesn't pass along any language options so the compiler doesn't know if e.g bare slash regex is enabled, resulting in the issue reported by https://forums.swift.org/t/regex-compiler-vs-repl/75393. We ought to add a language option parameter and pass along the language options for the REPL's SwiftASTContext.