Backport gh-156756 to Python 3.13. Retain replacement expressions in the tokenizer buffer instead of repeatedly copying the remaining source. Preserve the expression pointers when the buffer grows, and keep the interactive buffer while a formatted string is open.

Main already received the implementation through gh-156484, so the main commit only contains tests. This manual backport resolves the missing t-string test file and adapts the original fix to the release tokenizer and adds coverage for multiline interactive expressions, which otherwise abort in a debug build.

The targeted parser and command-line tests pass in a debug build, including the CPU-resource tests.

(cherry picked from commit c1df684)

• Issue: Quadratic compile() / ast.parse() time for modules with many f-strings (PEP 701 tokenizer update_fstring_expr rescans the whole remaining buffer per replacement field) #155525