Fixes missing files when manually building vscode server

[jeanp413]

This PR fixes #137568

[alexdima]

@mjbvz @joaomoreno The suggested change looks good to me, but I would like to get approval from you as well. Here is what I can put together:

• yarn extensions-ci is executed in the compilation phase
• extensions-ci is a gulp task that executes both compileExtensionsBuildTask and compileExtensionMediaBuildTask
• in gulpfile.vscode.reh.js, we would be calling in 1 place compileExtensionsBuildTask but not compileExtensionMediaBuildTask
• similarly, in gulpfile.vscode.js we would be calling in 3 places compileExtensionsBuildTask, but not compileExtensionMediaBuildTask
• this PR adds compileExtensionMediaBuildTask in 2 of the 4 places where compileExtensionsBuildTask was called

I plan that gulpfile.vscode.reh.js should do exactly what gulpfile.vscode.js does. So in this particular case, although issue #137568 talks about missing files in the server build, it looks like those files would be missing also in the vscode build (unless someone manually runs extensions-ci before).

I will therefore defer to you @joaomoreno @mjbvz to figure out what you want to do here and I am happy to take whatever you do also in gulpfile.reh.js.

[joaomoreno]

Thanks for the investigation @alexdima. This is the correct change. The changes in gulpfile.vscode.js should've been made at the time compileExtensionMediaBuildTask was introduced.

The *-ci tasks are running only in our CI which is orchestrated in a way that extensions-ci is always going to be called before vscode-*-ci.

[joaomoreno]

Thanks @jeanp413 🚀