Rollup merge of #113640 - jyn514:nodejs-defaults, r=GuillaumeGomez

Make `nodejs` control the default for RustdocJs tests instead of a hard-off switch

If someone says `x test rustdoc-js-std` explicitly on the command line, it's because they want to run the tests. Give an error instead of doing nothing and reporting success.

Before:
```
; x t rustdoc-js
No nodejs found, skipping "tests/rustdoc-js" tests
Build completed successfully in 0:00:00
```

After:
```
; x t rustdoc-js
thread 'main' panicked at 'need nodejs to run js-doc-test suite', test.rs:1566:13
Build completed unsuccessfully in 0:00:00
```

I recommend viewing the diff with whitespace changes disabled.

r? ````@GuillaumeGomez````

0 files changed, 0 insertions, 0 deletions