fix: invalid treemap iter advance

[silver-ymz]

The PR fixes following cases:

• After calling next(), jump forward 32 bits in the bitmap.
• After calling next_back(), jump backward in the bitmap.
• When the target bitmap does not exist, do not apply the invalid target's lower 32 bits to the next bitmap.
• Symmetric backward missing bitmap situation.

You can review the test cases for detailed information about these bugs.

[silver-ymz]

@Kerollmops Could you help to review it? Thank you very much!

[Kerollmops]

Hey @silver-ymz 👋

Thanks for the bug report and fix. Would it be possible to create two commits: one with the tests you added and another with the fix itself. Can you push them one after the other so that I can see the CI breaking on your first commit (the next tests failing) and the other become green as it fixes the tests, please?

Have a nice day 🌵

[silver-ymz]

cargo clippy failed due to a rust version update and is unrelated to this PR. It seems we need to first make clippy happy.