fix(extension/#2593): TabNine extension won't install

[bryphe]

Issue: The TabNine extension won't install (gives error - Unable to locate extension) and isn't usable

Defect: There were two blocking issues:

1. We weren't properly parsing the configuration setting format in the case of a null value - this was what caused the error (after install, we parse the package.json to get some metadata for showing info about the extension).
2. Once installed successfully, completions weren't showing up at all.

Fix:

1. Make the configuration parsing more general, to handle the null / optional value (Thanks @CrossR for the investigation!)
2. The completion provider uses a wildcard selector { pattern: '**' } so that it is triggered for all file types. However, we weren't recognizing this sort of selector - the second fix is to integrate glob pattern matching for these selectors.

This unblocks the first round of issues - I think there may be still a couple bugs to investigate:

1. The performance of completion seems to be slower w/ TabNine. Need to investigate if it's an issue on the Onivim side (ie, if there is a bottleneck merging a large amount of suggestions).
2. Some completions are adding duplicate text - similar to Completion - Sass: Completions with '@' result in duplicated character #2388
3. There's a special a webview configuration pane, that we can't show - since we don't have a webview in Revery. In the meantime, we should show a message or figure out another workaround.

Related #2583