localization: "Message ... didn't get externalized correctly"

## Problem

vscode extension host sometimes reports warnings of the form:

> Message ... didn't get externalized correctly.

## Solution?

Haven't confirmed, but based on https://github.com/microsoft/vscode/issues/42426 / https://github.com/microsoft/vscode-node-debug/commit/4d9a3a70fb776e05df218849a68cdfd2645d4ed0 we may need to do:

1. call `nls.loadMessageBundle()` directly in modules instead of using `src/shared/utilities/vsCodeUtils.ts:localize()`
2. remove `src/shared/utilities/vsCodeUtils.ts:localize()`

Start by reproducing the warning in the VS Code extension host, then inspect src/shared/utilities/vsCodeUtils.ts:localize() and the modules that use it. Compare the behavior with microsoft/vscode issue 42426 and the referenced vscode-node-debug commit. Done means the warning no longer appears and messages are externalized correctly.

Written by the indexing model from the issue text.