Document `inlineSuggestionVisible`, etc.

[Lemmingh]

Please add a definitive explanation of the contexts

• inlineSuggestionVisible
• inlineSuggestionHasIndentation
• hasOtherSuggestions
• hasSnippetCompletions

to api/references/when-clause-contexts. Thank you.

We find them critical when solving some problems, but have no idea what they are on earth:

• Conflict with Tab Completion yzhang-gh/vscode-markdown#665
• Respect Inline Suggestion to improve compatibility with GitHub Copilot yzhang-gh/vscode-markdown#1011
• Accepting co-pilot autocomplete for a markdown stopped working vscode#131953