rust: Write to .cargo/config.toml instead of .cargo/config

Seeing the following new warnings pop up on stderr when cargo was bumped
to 1.78:

```
warning: `/build/.cargo/config` is deprecated in favor of `config.toml`
note: if you need to support cargo 1.38 or earlier, you can symlink `config` to `config.toml`
```

which happens to break commitmsgfmt builds in nix (#320294).

closes #320294

pkgs/build-support/rust/fetch-cargo-tarball/default.nix

@@ -136,7 +136,7 @@ stdenv.mkDerivation (
 
       # Packages with git dependencies generate non-default cargo configs, so
       # always install it rather than trying to write a standard default template.
-      install -D $CARGO_CONFIG $name/.cargo/config;
+      install -D $CARGO_CONFIG $name/.cargo/config
 
       runHook postBuild
     '';

pkgs/build-support/rust/hooks/cargo-setup-hook.sh

@@ -22,7 +22,7 @@ cargoSetupPostUnpackHook() {
         mkdir .cargo
     fi
 
-    config="$cargoDepsCopy/.cargo/config";
+    config="$cargoDepsCopy/.cargo/config.toml"
     if [[ ! -e $config ]]; then
       config=@defaultConfig@
     fi;
@@ -30,9 +30,9 @@ cargoSetupPostUnpackHook() {
     tmp_config=$(mktemp)
     substitute $config $tmp_config \
       --subst-var-by vendor "$cargoDepsCopy"
-    cat ${tmp_config} >> .cargo/config
+    cat ${tmp_config} >> .cargo/config.toml
 
-    cat >> .cargo/config <<'EOF'
+    cat >> .cargo/config.toml <<'EOF'
     @cargoConfig@
 EOF
 

pkgs/build-support/rust/import-cargo-lock.nix

@@ -229,7 +229,7 @@ let
       else "cp $lockFileContentsPath $out/Cargo.lock"
     }
 
-    cat > $out/.cargo/config <<EOF
+    cat > $out/.cargo/config.toml <<EOF
 [source.crates-io]
 replace-with = "vendored-sources"
 
@@ -240,7 +240,7 @@ EOF
     declare -A keysSeen
 
     for registry in ${toString (builtins.attrNames extraRegistries)}; do
-      cat >> $out/.cargo/config <<EOF
+      cat >> $out/.cargo/config.toml <<EOF
 
 [source."$registry"]
 registry = "$registry"
@@ -256,7 +256,7 @@ EOF
         key=$(sed 's/\[source\."\(.*\)"\]/\1/; t; d' < "$crate/.cargo-config")
         if [[ -z ''${keysSeen[$key]} ]]; then
           keysSeen[$key]=1
-          cat "$crate/.cargo-config" >> $out/.cargo/config
+          cat "$crate/.cargo-config" >> $out/.cargo/config.toml
         fi
       fi
     done

pkgs/development/compilers/rust/rustc.nix

@@ -233,7 +233,7 @@ in stdenv.mkDerivation (finalAttrs: {
     export JEMALLOC_SYS_WITH_LG_VADDR=48
   '' + lib.optionalString (!(finalAttrs.src.passthru.isReleaseTarball or false)) ''
     mkdir .cargo
-    cat > .cargo/config <<\EOF
+    cat > .cargo/config.toml <<\EOF
     [source.crates-io]
     replace-with = "vendored-sources"
     [source.vendored-sources]

pkgs/development/ruby-modules/gem-config/default.nix

@@ -335,7 +335,7 @@ in
       rustc.unwrapped
     ];
     preBuild = ''
-      cat ../.cargo/config > ext/fast_mmaped_file_rs/.cargo/config.toml
+      cat ../.cargo/config.toml > ext/fast_mmaped_file_rs/.cargo/config.toml
       sed -i "s|cargo-vendor-dir|$PWD/../cargo-vendor-dir|" ext/fast_mmaped_file_rs/.cargo/config.toml
     '';
     postInstall = ''

pkgs/servers/clickhouse/default.nix

@@ -133,9 +133,9 @@ in mkDerivation rec {
     pushd rust
     cargoDeps="$rustDeps" cargoSetupPostUnpackHook
     rustDepsCopy="$cargoDepsCopy"
-    cat .cargo/config >> .cargo/config.toml.in
-    cat .cargo/config >> skim/.cargo/config.toml.in
-    rm .cargo/config
+    cat .cargo/config.toml >> .cargo/config.toml.in
+    cat .cargo/config.toml >> skim/.cargo/config.toml.in
+    rm .cargo/config.toml
     popd
 
     popd