Allow referencing version in wakeLanguageServer.path

[ag-eitilt]

With the extension now referencing an external installation, it can (usually) be easily pointed to the latest/current version on the machine as a proxy for "most likely to be the relevant version". However, since we track which exact version should be used in .wakeroot, we could theoretically be more specific on systems which additionally keep old/experimental versions alongside that, and have the extension automatically switch the version used based on the workspace it's operating in, without needing to manually set workspace-specific settings (which don't work for all workflows anyway).

We might not want to expose the user's full environment to the LSP, but processing a restricted set of %v replacements (something like /usr/share/wake/%v/bin/wake) seems like it could be nice for not only the wakeLanguageServer.path listed in the title, but also the wakeLanguageServer.standardLibrary to support all potential installation arrangements.

The issue label is a bit misleading: this is probably not a good first issue for someone just familiarizing themself with the codebase, but is likely a good second issue.