Activate extensions less eagerly

[gjsjohnmurray]

Currently the core extension and the bundled driver extensions all include * in their set of activationEvents.

They would be better VS Code citizens if they only activated when being used for the first time.

[gjsjohnmurray]

The four bundled drivers currently have this:

  "activationEvents": [
    "*",
    "onLanguage:sql",
    "onCommand:sqltools.*"
  ],

However the onCommand event doesn't yet support wildcards. See https://github.com/microsoft/vscode/issues/134373

[gjsjohnmurray]

Duplicate of #886