Support llmGenerated property on CodeAction

[StellaHuang95]

Addresses #1555

• Added llmGeneratedSupport to CodeActionClientCapabilities.
• Added llmGenerated to CodeAction.
• Added conversion logics in protocolConverter and codeConverter.
• Added the proposed api to the enabledApiProposals in package.json and the corresponding .d.ts file.

[dbaeumer]

Looking at the implementation now another boolean here feels wrong. I think we should follow the same approach as we did with other literals and add a tags field with CodeActionTag (like SymbolTag or CompletionItemTag). This make it homogenous with approaches we use somewhere else.

[dbaeumer]

Great work. Only some minor wording tweaks.