fix(install): Keep v1 file formatting the same

Inspired by rust-lang#10345, I looked for other cases where
`toml_edit::easy::to_string` is used (which outputs inline tables) to
see if we should switch to `to_string_pretty`.  The crates v1 file was
the only case I found.

As a side effect, we can no longer elide the empty `dev-dependencies`
table in published manifests.  This was the behavior before `toml_edit`,
so not much of a loss.

Author: epage

src/cargo/ops/common_for_install_and_uninstall.rs

@@ -356,7 +356,7 @@ impl CrateListingV1 {
         let mut file = lock.file();
         file.seek(SeekFrom::Start(0))?;
         file.set_len(0)?;
-        let data = toml::to_string(self)?;
+        let data = toml::to_string_pretty(self)?;
         file.write_all(data.as_bytes())?;
         Ok(())
     }

tests/testsuite/install.rs

@@ -990,7 +990,7 @@ Caused by:
 Caused by:
   TOML parse error at line 1, column 1
     |
-  1 | [..] = { \"foo 0.0.1 (registry+https://github.com/rust-lang/crates.io-index)\" = [\"foo[EXE]\"] }
+  1 | [..]
     | ^
   Unexpected `[..]`
   Expected key or end of input