Use i32 rather than usize as "default integer" in library template

`usize` was renamed from `uint` in order to convey that it's not the
"default integer type". Guide new users to use `i32` instead of `usize`.

Author: tbu-

src/cargo/ops/cargo_new.rs

@@ -876,7 +876,7 @@ fn main() {
 "
         } else {
             b"\
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }
 

tests/testsuite/cargo_init/auto_git/out/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }
 

tests/testsuite/cargo_init/formats_source/out/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
   left + right
 }
 

tests/testsuite/cargo_init/fossil_autodetect/out/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }
 

tests/testsuite/cargo_init/git_autodetect/out/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }
 

tests/testsuite/cargo_init/git_ignore_exists_no_conflicting_entries/out/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }
 

tests/testsuite/cargo_init/ignores_failure_to_format_source/out/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }
 

tests/testsuite/cargo_init/inherit_workspace_package_table/in/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }
 

tests/testsuite/cargo_init/inherit_workspace_package_table/out/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }
 

tests/testsuite/cargo_init/mercurial_autodetect/out/src/lib.rs

@@ -1,4 +1,4 @@
-pub fn add(left: usize, right: usize) -> usize {
+pub fn add(left: i32, right: i32) -> i32 {
     left + right
 }