[WD-8953] serve favicon for search engines separately from local folder

[akbarkz]

Done

Since favicons that are served from the Assets manager are not picked up by search engines and do not show in search results correctly (Google, Bing), we decided to try to serve it locally instead. Google asks for favicons that are divisible by 48px, so we only serve 48x48 locally. The rest are served from the Assets manager as before.

QA

Can be QA-ed only after merge and re-indexing in search engines.

Issue / Card

Fixes https://warthogs.atlassian.net/browse/WD-8953, https://github.com/canonical/canonical.com/issues/1161

[webteam-app]

Demo starting at https://canonical-com-1181.demos.haus

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (ff479ce) 66.55% compared to head (bd9196d) 66.55%. Report is 5 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1181 +/- ## ======================================= Coverage 66.55% 66.55% ======================================= Files 10 10 Lines 891 891 ======================================= Hits 593 593 Misses 298 298 ``` | [Flag](https://app.codecov.io/gh/canonical/canonical.com/pull/1181/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=canonical) | Coverage Δ | | |---|---|---| | [python](https://app.codecov.io/gh/canonical/canonical.com/pull/1181/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=canonical) | `66.55% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=canonical#carryforward-flags-in-the-pull-request-comment) to find out more.

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