Implement opt-in telemetry

[radeksimko]

Documentation is attached and also linked from the main Readme.

For transparency I'll just paste example events here also:

{
    "v": 1,
    "name": "initialize",
    "properties": {
        "experimentalCapabilities.referenceCountCodeLens": true,
        "lsVersion": "0.23.0",
        "options.commandPrefix": true,
        "options.excludeModulePaths": false,
        "options.experimentalFeatures.prefillRequiredFields": false,
        "options.experimentalFeatures.validateOnSave": false,
        "options.rootModulePaths": false,
        "options.terraformExecPath": false,
        "options.terraformExecTimeout": "",
        "options.terraformLogFilePath": false,
        "root_uri": "dir"
    }
}

{
    "v": 1,
    "name": "moduleData",
    "properties": {
        "backend": "remote",
        "backend.remote.hostname": "app.terraform.io",
        "installedProviders": {
            "registry.terraform.io/hashicorp/aws": "3.57.0",
            "registry.terraform.io/hashicorp/null": "3.1.0"
        },
        "moduleId": "8aa5a4dc-4780-2d90-b8fb-57de8288fb32",
        "providerRequirements": {
            "registry.terraform.io/hashicorp/aws": "",
            "registry.terraform.io/hashicorp/null": "~> 3.1"
        },
        "tfRequirements": "~> 1.0",
        "tfVersion": "1.0.7"
    }
}

---

This PR also lays down the foundation of hooks that can be then reused in #630

[jpogran]

Minor doc suggestions

[github-actions]

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