Use ajv standalone mode for schema validation

[sfc-gh-agrinevskij]

Is your enhancement related to a problem? Please describe.

Yaml language server currently uses ajv.compile for schema validation here: https://github.com/redhat-developer/yaml-language-server/blob/main/src/languageservice/services/yamlSchemaService.ts#L41 . This works fine, except for the cases, when unsafe-eval is disabled by CSP. This makes the language server unusable in this context. There are also a few discussions about that for ajv (for example ajv-validator/ajv#406).

Describe the solution you would like

AJV supports standalone mode https://ajv.js.org/standalone.html where a validation function is generated at compile time and doesn't rely on dynamic compilation anymore. I propose to switch the language server to use the standalone mode which would allow the server to work with strict CSP policies.