Only launch new instances of LS if it doesn't support multiple folders

[radeksimko]

The extension communicates via client capabilities that it supports multiple folders:

{
    "processId": 85078,
    "clientInfo": {
        "name": "vscode",
        "version": "1.56.0"
    },
    "rootPath": "/private/var/workspace/tf-test/github",
    "rootUri": "file:///private/var/workspace/tf-test/github",
    "capabilities": {
        "workspace": {
            "workspaceFolders": true,

this can also be seen by the client sending all opened folders, as expected in the initialize request:

    "workspaceFolders": [
        {
            "uri": "file:///private/var/workspace/tf-test/local",
            "name": "local"
        },
        {
            "uri": "file:///private/var/workspace/tf-test/netlify",
            "name": "netlify"
        },
        {
            "uri": "file:///private/var/workspace/tf-test/github",
            "name": "github"
        }
    ]

The LS therefore should have a way of opting into multi-folder mode via server capabilities and prevent the extension from launching more processes.

However when it does so:

{
    "capabilities": {
        "workspace": {
            "workspaceFolders": {
                "supported": true,
                "changeNotifications": "folder-change"
            }
        }

the extension still launches 3 instances of LS (1 for each of 3 folders) anyway.

WIP branch with experimental multi-folder support is available from hashicorp/terraform-ls#502

[github-actions]

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