Poll the terminals according to the buffer state

[pvdrz]

Describe the changes done on this pull request This PR changes the exec::pipe module so each side of the pipe is only polled if the buffer can handle the event:

• If the buffer is empty, then it is not possible to write any bytes to the writer.
• If the buffer is full, then it is not possible to read any bytes from the reader.

This also takes care of resuming the events when the buffer changes state.

Some changes were also made to the development logs so they are more useful:

• Use the panic location instead of macros so #[trace_caller] has effect on the logs.
• Log whenever a event is ready.

This PR is better reviewed on a commit-per-commit basis.

Pull Request Checklist

• [x] I have read and accepted the code of conduct for this project.
• [x] I have tested, formatted and ran clippy over my changes.
• [x] I have commented and documented my changes.
• [x] This pull request will fix #522 where a proper discussion about a solution has taken place.

[github-actions[bot]]

Number of dependencies and binary size impact report

Metric	main	PR #611	Delta
Direct dependencies	5	5	-
Total dependencies	10	10	-
Binary size	985.4 KiB	994 KiB	+0.9%
Text size	569.7 KiB	575 KiB	+0.9%

Dependencies diff

```diff └─ sudo-rs [v0.2.0-dev.20230627] ├─ glob [v0.3.1] ├─ libc [v0.2.147] ├─ log [v0.4.19] ├─ signal-hook [v0.3.15] | ├─ libc [v0.2.147] | ├─ signal-hook-registry [v1.4.1] | | └─ libc [v0.2.147] | └─ cc [v1.0.79] └─ signal-hook-registry [v1.4.1] ```

[codecov[bot]]

Codecov Report

Patch coverage: 96.34% and project coverage change: +0.07 :tada:

Comparison is base (6916363) 86.25% compared to head (16876e1) 86.33%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #611 +/- ## ========================================== + Coverage 86.25% 86.33% +0.07% ========================================== Files 62 62 Lines 8440 8480 +40 ========================================== + Hits 7280 7321 +41 + Misses 1160 1159 -1 ``` | [Impacted Files](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety) | Coverage Δ | | |---|---|---| | [src/log/mod.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL2xvZy9tb2QucnM=) | `85.71% <ø> (ø)` | | | [src/exec/use\_pty/pipe.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL2V4ZWMvdXNlX3B0eS9waXBlLnJz) | `95.97% <95.89%> (+2.33%)` | :arrow_up: | | [src/exec/event.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL2V4ZWMvZXZlbnQucnM=) | `83.13% <100.00%> (+0.20%)` | :arrow_up: | | [src/exec/no\_pty.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL2V4ZWMvbm9fcHR5LnJz) | `71.12% <100.00%> (+0.70%)` | :arrow_up: | | [src/exec/use\_pty/monitor.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL2V4ZWMvdXNlX3B0eS9tb25pdG9yLnJz) | `54.91% <100.00%> (+0.40%)` | :arrow_up: | | [src/exec/use\_pty/parent.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL2V4ZWMvdXNlX3B0eS9wYXJlbnQucnM=) | `74.40% <100.00%> (+0.23%)` | :arrow_up: | | [src/system/poll.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL3N5c3RlbS9wb2xsLnJz) | `98.07% <100.00%> (+1.92%)` | :arrow_up: | ... and [3 files with indirect coverage changes](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/611/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety)

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