Deduplicate std::process Default impl feature names

    error[E0711]: feature `process-exitcode-default` is declared stable since 1.74.0-beta.1, but was previously declared stable since 1.73.0
        --> library/std/src/process.rs:1964:1
         |
    1964 | #[stable(feature = "process-exitcode-default", since = "CURRENT_RUSTC_VERSION")]
         | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Author: dtolnay

library/std/src/process.rs

@@ -1594,7 +1594,7 @@ impl From<io::Stderr> for Stdio {
 pub struct ExitStatus(imp::ExitStatus);
 
 /// The default value is one which indicates successful completion.
-#[stable(feature = "process-exitcode-default", since = "1.73.0")]
+#[stable(feature = "process_exitstatus_default", since = "1.73.0")]
 impl Default for ExitStatus {
     fn default() -> Self {
         // Ideally this would be done by ExitCode::default().into() but that is complicated.
@@ -1961,7 +1961,7 @@ impl ExitCode {
 }
 
 /// The default value is [`ExitCode::SUCCESS`]
-#[stable(feature = "process-exitcode-default", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "process_exitcode_default", since = "CURRENT_RUSTC_VERSION")]
 impl Default for ExitCode {
     fn default() -> Self {
         ExitCode::SUCCESS