feat: speed up readers in the unmarshall path

[codecov[bot]]

Codecov Report

Patch coverage: 75.00% and project coverage change: -0.04% :warning:

Comparison is base (0b6ba93) 83.32% compared to head (2936d2e) 83.29%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #253 +/- ## ========================================== - Coverage 83.32% 83.29% -0.04% ========================================== Files 28 28 Lines 3269 3269 Branches 678 678 ========================================== - Hits 2724 2723 -1 Misses 330 330 - Partials 215 216 +1 ``` | [Files Changed](https://app.codecov.io/gh/Bluetooth-Devices/dbus-fast/pull/253?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bluetooth-Devices) | Coverage Δ | | |---|---|---| | [src/dbus\_fast/\_\_version\_\_.py](https://app.codecov.io/gh/Bluetooth-Devices/dbus-fast/pull/253?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bluetooth-Devices#diff-c3JjL2RidXNfZmFzdC9fX3ZlcnNpb25fXy5weQ==) | `0.00% <0.00%> (ø)` | | | [src/dbus\_fast/\_private/unmarshaller.py](https://app.codecov.io/gh/Bluetooth-Devices/dbus-fast/pull/253?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bluetooth-Devices#diff-c3JjL2RidXNfZmFzdC9fcHJpdmF0ZS91bm1hcnNoYWxsZXIucHk=) | `94.97% <100.00%> (+0.23%)` | :arrow_up: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/Bluetooth-Devices/dbus-fast/pull/253/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bluetooth-Devices)

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[bdraco]

CI seems happy. cython had a lot of bugs with cdef void before but they all appear to be fixed 🤞