test/py: Add a report show test durations

Execution time varies widely with the existing tests. Provides a way to
produce a summary of the time taken for each test, along with a
histogram.

This is enabled with the --timing flag.

Enable it for sandbox in CI.

Example:

   Duration : Number of tests
   ======== : ========================================
       <1ms :  1
       <8ms :  1
      <20ms : # 20
      <30ms : ######## 127
      <50ms : ######################################## 582
      <75ms : ####### 102
     <100ms : ## 39
     <200ms : ##### 86
     <300ms : # 29
     <500ms : ## 42
     <750ms : # 16
      <1.0s : # 15
      <2.0s : # 23
      <3.0s :  13
      <5.0s :  9
      <7.5s :  1
     <10.0s :  6
     <20.0s :  12

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

.gitlab-ci.yml

@@ -92,7 +92,7 @@ stages:
     # "${var:+"-k $var"}" expands to "" if $var is empty, "-k $var" if not
     - export PATH=/opt/qemu/bin:/tmp/uboot-test-hooks/bin:${PATH};
       export PYTHONPATH=/tmp/uboot-test-hooks/py/travis-ci;
-      ./test/py/test.py -ra --bd ${TEST_PY_BD} ${TEST_PY_ID}
+      ./test/py/test.py -ra --bd ${TEST_PY_BD} ${TEST_PY_ID} ${TEST_PY_EXTRA}
         ${TEST_PY_TEST_SPEC:+"-k ${TEST_PY_TEST_SPEC}"}
         --build-dir "$UBOOT_TRAVIS_BUILD_DIR"
         --junitxml=/tmp/${TEST_PY_BD}/results.xml
@@ -276,6 +276,7 @@ Check packing of Python tools:
 sandbox test.py:
   variables:
     TEST_PY_BD: "sandbox"
+    TEST_PY_EXTRA: "--timing"
   <<: *buildman_and_testpy_dfn
 
 sandbox with clang test.py: