Unsound usages of unsafe implementation from `buf` to `Page`

[llooFlashooll]

Hi, I am scanning the jammdb in the latest version with my own static analyzer tool.

Unsafe conversion found at: src/tx.rs#L329

if let TxLock::Rw(file) = &mut self.lock {
   // write meta page to file
   {
         let mut buf = vec![0; self.db.inner.pagesize as usize];

         #[allow(clippy::cast_ptr_alignment)]
         let page = unsafe { &mut *(&mut buf[0] as *mut u8 as *mut Page) };
         let meta_page_id = u64::from(self.meta.meta_page == 0);

This unsound implementation would create a misalignment issues if the type size of buf is smaller than the type size of Page.

This would potentially cause undefined behaviors in Rust. If we further manipulate the problematic converted types, it would potentially lead to different consequences such as access out-of-bound. I am reporting this issue for your attention.