[3.13] gh-125096: Don't import _pyrepl in site if PYTHON_BASIC_REPL (#125097) (#125111)

gh-125096: Don't import _pyrepl in site if PYTHON_BASIC_REPL (#125097)

If the PYTHON_BASIC_REPL environment variable is set, the site module
no longer imports the _pyrepl module.

Moreover, the site module now respects -E and -I command line
options: ignore PYTHON_BASIC_REPL in this case.

(cherry picked from commit 65ce228d63878d8b6d0005f682e89ad9d5289c4b)