[7.17] Update to Node 20 and setup-node@v4

[pquentin]

I checked manually that the commands still work, even if ts-standard now complains that the TypeScript version is too recent:

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WARNING: You are currently running a version of TypeScript which is not officially supported by @typescript-eslint/typescript-estree.                         
                                                                                                                                                              
You may find that it works just fine, or you may not.                                                                                                         
                                                                                                                                                              
SUPPORTED TYPESCRIPT VERSIONS: >=3.3.1 <4.5.0                                                                                                                 
                                                                                                                                                              
YOUR TYPESCRIPT VERSION: 4.5.5                                                                                                                                
                                                                                                                                                              
Please only submit bug reports when using the officially supported version.                                                                                   
                                                                                                                                                              
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But this should fix Generate output failures: https://github.com/elastic/elasticsearch-specification/actions/runs/9775028082