chore: invalid empty bundle types filtered from result

[WillieRuemmele]

What does this PR do?

if a there was an empty top level directory for a bundle type, I'll use LWC as an example, it would cause deploy errors. I filter those out during the bundle adapter's populate method

so a force:source:deploy -m LightningComponentBundle
on a dir that looks like

   * ├── validLWC/
   * |   ├── myFoo.js
   * |   ├── myFooStyle.css
   * |   ├── myFoo.html
   * |   ├── myFoo.js-meta.xml
   * ├── invalidLWC/

will only result in validLWC being deployed, and no errors

What issues does this PR fix or reference?

#forcedotcom/cli#1099, @W-9692466@

Functionality Before

error on the server An object 'withoutContent' of type LightningComponentBundle was named in package.xml, but was not found in zipped directory
<insert gif and/or summary>

Functionality After

deploys correctly
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[WillieRuemmele]

LGTM, thanks @shetzel

[shetzel]

Verified unit test fails without the code fix and passes with it.
Verified the fix works using the ebikes_lwc project, with and without an empty LWC directory.
Code looks good with nice jsdoc comments branched from develop.