DOC: Added np.show_runtime (#21468)

doc/release/upcoming_changes/21468.new_feature.rst

@@ -0,0 +1,60 @@
+New function `np.show_runtime`
+------------------------------
+
+A new function ``np.show_runtime`` has been added to display the runtime
+information of the machine in addition to ``np.show_config`` which displays
+the build-related information.
+This function returns a list of dictionaries as follows::
+
+    >>> np.show_runtime()
+    [{'simd_extensions': {'baseline': ['SSE', 'SSE2', 'SSE3'],
+                          'found': ['SSSE3',
+                                    'SSE41',
+                                    'POPCNT',
+                                    'SSE42',
+                                    'AVX',
+                                    'F16C',
+                                    'FMA3',
+                                    'AVX2'],
+                          'not_found': ['AVX512F',
+                                        'AVX512CD',
+                                        'AVX512_KNL',
+                                        'AVX512_KNM',
+                                        'AVX512_SKX',
+                                        'AVX512_CLX',
+                                        'AVX512_CNL',
+                                        'AVX512_ICL']}},
+     {'architecture': 'Zen',
+      'filepath': '/usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.20.so',
+      'internal_api': 'openblas',
+      'num_threads': 12,
+      'prefix': 'libopenblas',
+      'threading_layer': 'pthreads',
+      'user_api': 'blas',
+      'version': '0.3.20'}]
+
+Note that this function requires `threadpoolctl`_ to function properly.
+It would result in the following warning if not installed::
+
+    >>> np.show_runtime()
+    WARNING: `threadpoolctl` not found in system! Install it by `pip install threadpoolctl`. Once installed, try `np.show_runtime` again for more detailed build information
+    [{'simd_extensions': {'baseline': ['SSE', 'SSE2', 'SSE3'],
+                          'found': ['SSSE3',
+                                    'SSE41',
+                                    'POPCNT',
+                                    'SSE42',
+                                    'AVX',
+                                    'F16C',
+                                    'FMA3',
+                                    'AVX2'],
+                          'not_found': ['AVX512F',
+                                        'AVX512CD',
+                                        'AVX512_KNL',
+                                        'AVX512_KNM',
+                                        'AVX512_SKX',
+                                        'AVX512_CLX',
+                                        'AVX512_CNL',
+                                        'AVX512_ICL']}}]
+
+
+.. _threadpoolctl: https://pypi.org/project/threadpoolctl/