fix(lsp): handle ShowDocumentParams.external

[justinmk3]

Problem

LSP server can't open URLs, because the LSP client does not correctly handle ShowDocumentParams.external requests.
LSP spec: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#showDocumentParams

Solution

When ShowDocumentParams.external is true, open the URL in a web browser instead of as a editor document.

Also: avoid PII in openUrl metric.

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