Replace 'memoffset' crate with core functionality (#12761)

The `std::mem::offset_of` macro was introduced in Rust 1.77.0.

In the passing, mark the function as `const`, as suggested in the
comment. Not sure which compiler version that requires, but it works
with what have currently.

libs/postgres_ffi/Cargo.toml

@@ -12,7 +12,6 @@ crc32c.workspace = true
 criterion.workspace = true
 once_cell.workspace = true
 log.workspace = true
-memoffset.workspace = true
 pprof.workspace = true
 thiserror.workspace = true
 serde.workspace = true

libs/postgres_ffi/src/controlfile_utils.rs

@@ -34,9 +34,8 @@ const SIZEOF_CONTROLDATA: usize = size_of::<ControlFileData>();
 impl ControlFileData {
     /// Compute the offset of the `crc` field within the `ControlFileData` struct.
     /// Equivalent to offsetof(ControlFileData, crc) in C.
-    // Someday this can be const when the right compiler features land.
-    fn pg_control_crc_offset() -> usize {
-        memoffset::offset_of!(ControlFileData, crc)
+    const fn pg_control_crc_offset() -> usize {
+        std::mem::offset_of!(ControlFileData, crc)
     }
 
     ///