Don't lint cast_ptr_alignment when used for unaligned reads and writes

[Jarcho]

fixes #2881

Ideally this would trace the usage of the value rather than only looking at the parent expression, but that would require dataflow analysis. e.g.

let x = ptr as *const u16;
c.read_unaligned(x);

Arch specific intrinsic functions need to be checked for ones which could take an unaligned pointer. This can be another PR.

changelog: Don't lint cast_ptr_alignment when used for unaligned reads and writes

[rust-highfive]

r? @llogiq

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[llogiq]

Thank you! Great as always, a joy to review.

@bors r+

[bors]

📌 Commit e4fc15e has been approved by llogiq

[bors]

⌛ Testing commit e4fc15e with merge 9fd1cde...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing 9fd1cde to master...