Update to 0.4.0

[frengor]

• Update version to 0.4.0
• Improve the ergonomics of weak pointers
  • Remove Weakable and WeakableCc
  • Add Weak::new()
  • Rename weak-ptr feature to weak-ptrs
• Implement common traits like Display, PartialEq, Eq, Hash, etc.
• Code clean up and smaller improvements

[github-actions]

Benchmark results:

bench::stress_tests_group::stress_test_bench seed:0xCAFE
  Instructions:            89071605 (-0.531920%)
  L1 Hits:                129075062 (-0.050827%)
  L2 Hits:                  1680518 (+0.035418%)
  RAM Hits:                   93701 (No Change)
  Total read+write:       130849281 (-0.049684%)
  Estimated Cycles:       140757187 (-0.044499%)
bench::binary_trees_group::count_binary_trees_bench depth:11
  Instructions:            90042632 (-1.106861%)
  L1 Hits:                133594437 (-0.444117%)
  L2 Hits:                   243775 (+2.458327%)
  RAM Hits:                    2105 (+0.047529%)
  Total read+write:       133840317 (-0.438973%)
  Estimated Cycles:       134886987 (-0.418359%)
bench::binary_trees_group::count_binary_trees_with_parent_bench depth:11
  Instructions:           167873861 (-3.287451%)
  L1 Hits:                248160682 (-3.239631%)
  L2 Hits:                  1533714 (+0.413382%)
  RAM Hits:                    3953 (+0.101291%)
  Total read+write:       249698349 (-3.217954%)
  Estimated Cycles:       255967607 (-3.132307%)
bench::linked_lists_group::large_linked_list_bench size:4096
  Instructions:            96429296 (-2.121390%)
  L1 Hits:                142282864 (-1.531784%)
  L2 Hits:                  1830046 (+0.000984%)
  RAM Hits:                   10065 (+0.029815%)
  Total read+write:       144122975 (-1.512508%)
  Estimated Cycles:       151785369 (-1.437140%)

Old results:

bench::stress_tests_group::stress_test_bench seed:0xCAFE
  Instructions:            89547928
  L1 Hits:                129140700
  L2 Hits:                  1679923
  RAM Hits:                   93701
  Total read+write:       130914324
  Estimated Cycles:       140819850
bench::binary_trees_group::count_binary_trees_bench depth:11
  Instructions:            91050434
  L1 Hits:                134190400
  L2 Hits:                   237926
  RAM Hits:                    2104
  Total read+write:       134430430
  Estimated Cycles:       135453670
bench::binary_trees_group::count_binary_trees_with_parent_bench depth:11
  Instructions:           173580226
  L1 Hits:                256469343
  L2 Hits:                  1527400
  RAM Hits:                    3949
  Total read+write:       258000692
  Estimated Cycles:       264244558
bench::linked_lists_group::large_linked_list_bench size:4096
  Instructions:            98519274
  L1 Hits:                144496234
  L2 Hits:                  1830028
  RAM Hits:                   10062
  Total read+write:       146336324
  Estimated Cycles:       153998544

---

Results without finalization:

bench::stress_tests_group::stress_test_bench seed:0xCAFE
  Instructions:            86489839 (-2.839796%)
  L1 Hits:                124556401 (-3.047155%)
  L2 Hits:                  1669325 (+0.036075%)
  RAM Hits:                   93690 (-0.005336%)
  Total read+write:       126319416 (-3.005460%)
  Estimated Cycles:       136182176 (-2.792323%)
bench::binary_trees_group::count_binary_trees_bench depth:11
  Instructions:            89007609 (-0.573524%)
  L1 Hits:                132039713 (-0.577461%)
  L2 Hits:                   244606 (-0.217428%)
  RAM Hits:                    2105 (+0.047529%)
  Total read+write:       132286424 (-0.576787%)
  Estimated Cycles:       133336418 (-0.573827%)
bench::binary_trees_group::count_binary_trees_with_parent_bench depth:11
  Instructions:           123364636 (-3.360653%)
  L1 Hits:                183382700 (-3.421538%)
  L2 Hits:                   874497 (+0.032029%)
  RAM Hits:                    3943 (-0.025355%)
  Total read+write:       184261140 (-3.405641%)
  Estimated Cycles:       187893190 (-3.341469%)
bench::linked_lists_group::large_linked_list_bench size:4096
  Instructions:            70865765 (-3.836134%)
  L1 Hits:                104807102 (-3.725700%)
  L2 Hits:                   960739 (-0.014882%)
  RAM Hits:                   10050 (-0.019897%)
  Total read+write:       105777891 (-3.692897%)
  Estimated Cycles:       109962547 (-3.557903%)

Old results without finalization:

bench::stress_tests_group::stress_test_bench seed:0xCAFE
  Instructions:            89017762
  L1 Hits:                128471115
  L2 Hits:                  1668723
  RAM Hits:                   93695
  Total read+write:       130233533
  Estimated Cycles:       140094055
bench::binary_trees_group::count_binary_trees_bench depth:11
  Instructions:            89521034
  L1 Hits:                132806619
  L2 Hits:                   245139
  RAM Hits:                    2104
  Total read+write:       133053862
  Estimated Cycles:       134105954
bench::binary_trees_group::count_binary_trees_with_parent_bench depth:11
  Instructions:           127654667
  L1 Hits:                189879500
  L2 Hits:                   874217
  RAM Hits:                    3944
  Total read+write:       190757661
  Estimated Cycles:       194388625
bench::linked_lists_group::large_linked_list_bench size:4096
  Instructions:            73692716
  L1 Hits:                108863011
  L2 Hits:                   960882
  RAM Hits:                   10052
  Total read+write:       109833945
  Estimated Cycles:       114019241