bpo-42856: Add --with-wheel-pkg-dir=PATH configure option (GH-24210)

Add --with-wheel-pkg-dir=PATH option to the ./configure script. If
specified, the ensurepip module looks for setuptools and pip wheel
packages in this directory: if both are present, these wheel packages
are used instead of ensurepip bundled wheel packages.

Some Linux distribution packaging policies recommend against bundling
dependencies. For example, Fedora installs wheel packages in the
/usr/share/python-wheels/ directory and don't install the
ensurepip._bundled package.

ensurepip: Remove unused runpy import.
diff --git a/configure b/configure
index 1d81c00..37ee369 100755
--- a/configure
+++ b/configure
@@ -630,6 +630,7 @@
 ENSUREPIP
 SRCDIRS
 THREADHEADERS
+WHEEL_PKG_DIR
 LIBPL
 PY_ENABLE_SHARED
 PLATLIBDIR
@@ -847,6 +848,7 @@
 with_libc
 enable_big_digits
 with_platlibdir
+with_wheel_pkg_dir
 with_computed_gotos
 with_ensurepip
 with_openssl
@@ -1576,6 +1578,9 @@
                           system-dependent)
   --with-platlibdir=DIRNAME
                           Python library directory name (default is "lib")
+  --with-wheel-pkg-dir=PATH
+                          Directory of wheel packages used by ensurepip
+                          (default: none)
   --with-computed-gotos   enable computed gotos in evaluation loop (enabled by
                           default on supported compilers)
   --with-ensurepip[=install|upgrade|no]
@@ -15493,6 +15498,29 @@
 fi
 
 
+# Check for --with-wheel-pkg-dir=PATH
+
+WHEEL_PKG_DIR=""
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-wheel-pkg-dir" >&5
+$as_echo_n "checking for --with-wheel-pkg-dir... " >&6; }
+
+# Check whether --with-wheel-pkg-dir was given.
+if test "${with_wheel_pkg_dir+set}" = set; then :
+  withval=$with_wheel_pkg_dir;
+if test -n "$withval"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+  WHEEL_PKG_DIR="$withval"
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
 # Check whether right shifting a negative integer extends the sign bit
 # or fills with zeros (like the Cray J90, according to Tim Peters).
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether right shift extends the sign bit" >&5