Add `Attribute::read_raw`.

[codecov[bot]]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (b0b4455) 86.13% compared to head (a71b024) 86.14%. Report is 2 commits behind head on master.

Files	Patch %	Lines
src/examples/read_write_raw_ptr.cpp	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #940 +/- ## ========================================== + Coverage 86.13% 86.14% +0.01% ========================================== Files 89 90 +1 Lines 5855 5861 +6 ========================================== + Hits 5043 5049 +6 Misses 812 812 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.