fix: Fix local datafusion-cli test failure (#21761)

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## Rationale for this change

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One test case in `datafusion-cli` crate is failing locally if you run
all tests through `cargo nextest run`, but passes for `cargo test`

```
        FAIL [   0.375s] datafusion-cli::cli_integration cli_explain_environment_overrides
```

The reason is `nextest` triggers a different build graph, which enforces
a feature flag in `serde_json` dependency.

This PR enforces this feature in the `dev-dependencies` in
`datafusion-cli` crate, so the test become deterministic under different
test setup.

#21502 Fixed a similar issue,
and also explains why not enabling it in the global dependencies inside
`Cargo.toml`

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Author: 2010YOUY01

Cargo.lock

@@ -78,3 +78,11 @@ insta = { workspace = true }
 insta-cmd = "0.6.0"
 rstest = { workspace = true }
 testcontainers-modules = { workspace = true, features = ["minio"] }
+# Makes sure `test_display_pg_json` behaves in a consistent way regardless of
+# feature unification with dependencies
+serde_json = { workspace = true, features = ["preserve_order"] }
+
+# Required because we pull serde_json with a feature to get consistent pg display,
+# but its not directly used.
+[package.metadata.cargo-machete]
+ignored = "serde_json"

datafusion-cli/Cargo.toml

@@ -18,19 +18,19 @@ exit_code: 0
 | logical_plan | [                                       |
 |              |   {                                     |
 |              |     "Plan": {                           |
-|              |       "Expressions": [                  |
-|              |         "Int64(123)"                    |
-|              |       ],                                |
 |              |       "Node Type": "Projection",        |
-|              |       "Output": [                       |
+|              |       "Expressions": [                  |
 |              |         "Int64(123)"                    |
 |              |       ],                                |
 |              |       "Plans": [                        |
 |              |         {                               |
 |              |           "Node Type": "EmptyRelation", |
-|              |           "Output": [],                 |
-|              |           "Plans": []                   |
+|              |           "Plans": [],                  |
+|              |           "Output": []                  |
 |              |         }                               |
+|              |       ],                                |
+|              |       "Output": [                       |
+|              |         "Int64(123)"                    |
 |              |       ]                                 |
 |              |     }                                   |
 |              |   }                                     |