Convert ruuvitag_ble to a brand used for both ruuvi_gateway and ruuvitag_ble

[akx]

Proposed change

Moves core_integrations/ruuvitag_ble to core_brands/ruuvi and symlinks it for the ruuvitag_ble integration and ruuvi_gateway(home-assistant/core#84853).

Type of change

• Add a new logo or icon for a new core integration
• Add a missing icon or logo for an existing core integration
• Add a new logo or icon for a custom integration (custom component)
  • I've opened up a PR for my custom integration on the Home Assistant
    Python wheels repository
• Replace an existing icon or logo with a higher quality version
• Removing an icon or logo

Additional information

• Link to code base pull request: Ruuvi Gateway integration core#84853
• Link to documentation pull request: Docs for new Ruuvi Gateway integration home-assistant.io#25480
• Link to integration documentation on our website: n/a

Checklist

• The added/replaced image(s) are PNG
• Icon image size is 256x256px (icon.png)
• hDPI icon image size is 512x512px for (icon@2x.png)
• Logo image size has min 128px, but max 256px, on the shortest side (logo.png)
• hDPI logo image size has min 256px, but max 512px, on the shortest side (logo@2x.png)

[frenck]

✅ Approved. Can be merged as soon as the parent PR gets merged.

[akx]

@frenck Parent PRs have been merged :)