Add linterOptions to settings

[wata727]

Part of #334
Fixes #855

This PR adds linterOptions to the language server settings. This includes the following TFLint configs, which I plan to use in subsequent PRs:

• options.linters.tflint.path
• options.linters.tflint.configPath
• options.linters.tflint.lintOnSave
• options.linters.tflint.timeout

Please note that this change differs from that proposed in #855 in the following points:

• The binaryPath has been changed to path to match options.terraform.path.
• The binaryFlags is not supported. TFLint has multiple flags, and I'm not yet sure if they can be safely passed through terraform-ls.
  • However, since --config is likely to be needed at an early stage, only configPath is supported.
• The timeout is added. Because TFLint rules can be extended, it is necessary to set a timeout to ensure completion.
• Just like Terraform, binary path is only validated to make sure it is accessible, not executable.
• If validation fails, it returns an error instead of silently failing, which is probably better if you set the path explicitly.

Whether these changes are appropriate is open to debate. I would be happy to discuss it here.
If there are any other matters that need to be discussed in advance regarding this issue, please feel free to let me know. Thank you.