Upgrade VS Code yaml from 0.14.0 to 0.18.0

[apupier]

Is your enhancement related to a problem? Please describe.

it contains several bugfixes and enahncements https://marketplace.visualstudio.com/items/redhat.vscode-yaml/changelog
https://github.com/eclipse-che/che-plugin-registry/blob/13ab2ea940452ef1f07b7145702d9dc081709885/che-theia-plugins.yaml#L336

nota: a lot of other extensions relies on even older versions. For instance OpenShift connector https://github.com/eclipse-che/che-plugin-registry/blob/13ab2ea940452ef1f07b7145702d9dc081709885/che-theia-plugins.yaml#L331

Describe the solution you'd like

Describe alternatives you've considered

Additional context

[ericwill]

We need the VS Code version to be 1.52 first, as vscode-yaml depends on that: redhat-developer/vscode-yaml#471

Theia issue: eclipse-theia/theia#9193

[apupier]

VS Code API 1.52 seems now available as eclipse-theia/theia#9193 is closed
latest VS COde yaml is now 1.2.2 and still declares vs code 1.52 as minimal version required https://github.com/redhat-developer/vscode-yaml/blob/ca93afaf6867731d349e2cfef954da9f9e01786d/package.json#L27

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