rust: fix unit test link error on Rust 1.70

Rust 1.70 appears to now link code on both branches of `if cfg!(test)`
now causing Rust unit tests to fail as that pattern was used to
disable functions only available when linked with the Suricata C code.

To work-around this issue, provide two versions of the `new` function,
one for unit tests and one when running as an application.

rust/src/frames.rs

@@ -17,9 +17,11 @@
 
 use crate::applayer::StreamSlice;
 use crate::core::Flow;
+#[cfg(not(test))]
 use crate::core::STREAM_TOSERVER;
 use crate::core::Direction;
 
+#[cfg(not(test))]
 #[repr(C)]
 struct CFrame {
     _private: [u8; 0],
@@ -27,6 +29,7 @@ struct CFrame {
 
 // Defined in app-layer-register.h
 extern {
+    #[cfg(not(test))]
     fn AppLayerFrameNewByRelativeOffset(
         flow: *const Flow, stream_slice: *const StreamSlice, frame_start_rel: u32, len: i64,
         dir: i32, frame_type: u8,
@@ -34,6 +37,7 @@ extern {
     fn AppLayerFrameAddEventById(flow: *const Flow, dir: i32, id: i64, event: u8);
     fn AppLayerFrameSetLengthById(flow: *const Flow, dir: i32, id: i64, len: i64);
     fn AppLayerFrameSetTxIdById(flow: *const Flow, dir: i32, id: i64, tx_id: u64);
+    #[cfg(not(test))]
     fn AppLayerFrameGetId(frame: *const CFrame) -> i64;
 }
 
@@ -49,6 +53,7 @@ impl std::fmt::Debug for Frame {
 }
 
 impl Frame {
+    #[cfg(not(test))]
     #[allow(clippy::not_unsafe_ptr_arg_deref)]
     pub fn new(
         flow: *const Flow, stream_slice: &StreamSlice, frame_start: &[u8], frame_len: i64,
@@ -56,9 +61,6 @@ impl Frame {
     ) -> Option<Self> {
         let offset = frame_start.as_ptr() as usize - stream_slice.as_slice().as_ptr() as usize;
         SCLogDebug!("offset {} stream_slice.len() {} frame_start.len() {}", offset, stream_slice.len(), frame_start.len());
-        // If running Rust unit tests this won't be compiled and None will be returned, as we don't
-        // have the Suricata C code available for linkage.
-        if cfg!(not(test)) {
         let frame = unsafe {
             AppLayerFrameNewByRelativeOffset(
                 flow,
@@ -78,9 +80,17 @@ impl Frame {
         } else {
             None
         }
-        } else {
-            None
     }
+
+    /// A variation of `new` for use when running Rust unit tests as
+    /// the C functions for building a frame are not available for
+    /// linkage.
+    #[cfg(test)]
+    pub fn new(
+        _flow: *const Flow, _stream_slice: &StreamSlice, _frame_start: &[u8], _frame_len: i64,
+        _frame_type: u8,
+    ) -> Option<Self> {
+        None
     }
 
     /// Conversion function to get the direction in the correct form for the