Use inline SVG for drawer Drupal logo

Converts logo.svg from file-system into 'data:image/svg+xml' in navigation_theme. also means we are not using extension.list.module service in template hook.

re: current summary request.
moving to data does not change img alt (role) or any current css as is still just an image.

other standing work with custom logo will apply still this way!

Thanks for working on this! But I'm not sure about this: moving markup to a .module file makes things strange: as a themer, I'd expect this in a template itself with the rest of the elements if it's not an image. It works? Yes. Is this the expected place for this? Nope :)
I'd go just add the SVG on the navigation.html.twig template and add any required logic there if the logo is replaced by a custom image or hidden.

-this is completely removing the IMG tag. this will break #3436526: Adjust custom navigation logo dimensions on upload.

------
@bronzehedwick. somewhere between. (:

 */
function navigation_theme($existing, $type, $theme, $path) {
[remove first lines]
 ....

  $items['navigation'] = [
    'variables' => [
      'hide_logo' => FALSE,
      'logo_path' => FALSE,    <--
      'logo_width' => 40,
      'logo_height' => 40,
      'menu_content' => [],
      'menu_footer' => [],
    ],
  ];

-. make path empty.
- if twig sees empty load 'new icon twig' into PATH, otherwise PATH would be a custom logo (passed by NaviagaionRenderer if user has chosen to adds an icon).
- then url encode the 'the svg load' in twig to be ready as image data. this would keep the template readable.

thanks!
looks good. I'll move to RTBC!

-----

if we want to come back about sending to data (always only image tag) , this would be a sample for the logo.svg.twig contents

{% set svg_content %}
{% apply spaceless %}
<svg xmlns="http://www.w3.org/2000/svg" width="{{ width|default(40) }}" height="{{ height|default(40) }}" viewBox="0 0 32 32">
  <rect fill="{{ bg_color|default('#347efe') }}" width="32" height="32" rx="8"/>
  <path fill="{{ fg_color|default('#fff') }}" d="M19,10.3C17.67,9,16.38,7.68,16,6.23,15.62,7.67,14.33,9,13,10.3c-2,2-4.31,4.31-4.31,7.74a7.32,7.32,0,0,0,14.64,0C23.32,14.61,21,12.32,19,10.3Zm-7.22,9.44c-.45,0-2.11-2.87,1-5.91l2,2.22a.18.18,0,0,1,0,.25h0A19.3,19.3,0,0,0,12,19.6C11.92,19.75,11.83,19.74,11.79,19.74ZM16,23.51A2.52,2.52,0,0,1,13.48,21a2.56,2.56,0,0,1,.63-1.66c.45-.56,1.89-2.12,1.89-2.12s1.41,1.59,1.89,2.11A2.5,2.5,0,0,1,18.52,21,2.52,2.52,0,0,1,16,23.51Zm4.82-4.09c-.06.12-.18.32-.35.33s-.32-.14-.55-.47c-.48-.71-4.67-5.09-5.46-5.94s-.09-1.27.18-1.55L16,10.44a35.72,35.72,0,0,1,4.25,4.8A4.5,4.5,0,0,1,20.82,19.42Z"/>
</svg>
{% endapply %}
{% endset %}
data:image/svg+xml,{{ svg_content|url_encode }}

@bronzehedwick
- moving width/height to var seems not needed [as this doesn't recenter, re-size the actual paths]
- also noticed viewbox is "0 0 32 32" -- i think should be 40?\

I'm assuming the color var would be useful for light/dark modes down the road, indeed could be useful.

width="{{ width|default(40) }}" height="{{ height|default(40) }}"
we just don't need to be allowing the size to be changed. some one could send in a smaller size than the viewbox.

re:viewbox. -- i've just got thrown off in my own head (viewport of svg)

nice.

This has a conflict with previous changes merged. Needs to be updated

Thanks for the merge conflict resolution @bronzehedwick. Looks good to me.

Merged to 1.x 🎉. Thanks!