[style](trx-rs): fix clippy warnings for -D warnings CI

The CI lint job runs clippy with -D warnings, which surfaced a set of
existing warnings across decoders, the client, and the soapysdr backend.
Resolve them so the workspace is clean under the enforced lint level:

- collapsible_match / identity_op / needless_range_loop / same_item_push
  in trx-rds, trx-wspr, trx-vdes, trx-wefax, trx-aprs (mostly tests)
- field_reassign_with_default -> struct-update syntax in trx-client config
  tests
- assign_op_pattern, useless vec!, and test-module ordering picked up by
  cargo clippy --fix in trx-client and the soapysdr WFM tests

No behaviour changes; all affected crates' tests pass.

Assisted-By: Claude Code (claude-opus-4)
Claude-Session: https://claude.ai/code/session_01NFpGtGTWUEYXLwZeZs2RAV
Signed-off-by: Stan Grams <sjg@haxx.space>

src/decoders/trx-vdes/src/crc.rs

@@ -134,9 +134,7 @@ mod tests {
             .flat_map(|&b| (0..8).rev().map(move |i| (b >> i) & 1))
             .collect();
         // Append wrong CRC
-        for _ in 0..16 {
-            bits.push(0);
-        }
+        bits.resize(bits.len() + 16, 0);
         assert!(!check_crc16(&bits));
     }
 

src/decoders/trx-vdes/src/link_layer.rs

@@ -346,8 +346,8 @@ mod tests {
         write_bits(&mut bits, 12, 32, 123456); // source_id
         write_bits(&mut bits, 44, 11, 20); // data_count = 20
                                            // Fill some payload
-        for i in 55..75 {
-            bits[i] = (i % 2) as u8;
+        for (i, bit) in bits.iter_mut().enumerate().take(75).skip(55) {
+            *bit = (i % 2) as u8;
         }
         append_crc(&mut bits);