[LIT] Print discovered tests and percentages

[madhur13490]

Summary

This patch adds "nice-to-have" feature in lit.
it prints the total number of discovered tests at the beginning.
It is covenient to see the total number of tests and avoid
scrolling up to the beginning of log.

Further, this patch also prints %ge of tests.

llvm/utils/lit/lit/main.py

test_times = [
         (t.getFullName(), t.result.elapsed) for t in tests if t.result.elapsed
     ]
     if test_times:
         lit.util.printHistogram(test_times, title="Tests")
 
 
 def print_results(tests, elapsed, opts):
     tests_by_code = {code: [] for code in lit.Test.ResultCode.all_codes()}
+    total_tests = len(tests)
     for test in tests:
         tests_by_code[test.result.code].append(test)
 
     for code in lit.Test.ResultCode.all_codes():
         print_group(
             sorted(tests_by_code[code], key=lambda t: t.getFullName()),
             code,
             opts.shown_codes,
         )
 
-    print_summary(tests_by_code, opts.quiet, elapsed)
+    print_summary(total_tests, tests_by_code, opts.quiet, elapsed)
 
 
 def print_group(tests, code, shown_codes):
     if not tests:
         return
     if not code.isFailure and code not in shown_codes:
         return
     print("*" * 20)
     print("{} Tests ({}):".format(code.label, len(tests)))
     for test in tests:
         print("  %s" % test.getFullName())
     sys.stdout.write("\n")
 
 
-def print_summary(tests_by_code, quiet, elapsed):
+def print_summary(total_tests, tests_by_code, quiet, elapsed):
     if not quiet:
         print("\nTesting Time: %.2fs" % elapsed)
 
+    print("\nTotal Discovered Tests: %s" %(total_tests))
     codes = [c for c in lit.Test.ResultCode.all_codes() if not quiet or c.isFailure]
     groups = [(c.label, len(tests_by_code[c])) for c in codes]
     groups = [(label, count) for label, count in groups if count]
     if not groups:
         return
 
     max_label_len = max(len(label) for label, _ in groups)
     max_count_len = max(len(str(count)) for _, count in groups)
 
     for (label, count) in groups:
         label = label.ljust(max_label_len)
         count = str(count).rjust(max_count_len)
-        print("  %s: %s" % (label, count))
+        print("  %s: %s (%.2f%%)" % (label, count, float(count) / total_tests * 100))