New CI color and background image

[phil-davis]

Description

This PR changes the CI color project wide and adds a new background image for the login screen.
This will adapt ownCloud to the new style guide.

How Has This Been Tested?

• manually tested

Screenshots (if appropriate):

Types of changes

• Non-breaking change
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:
• Changelog item, see TEMPLATE

[phil-davis]

This is an updated version of #37628 with a better core/img/background.jpg that does not cause problems in the UI acceptance tests.

PR #37649 has commits that demonstrated the problem with the previous core/img/background.jpg and that the new one passes.

[codecov]

Codecov Report

Merging #37650 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master   #37650   +/-   ##
=========================================
  Coverage     64.74%   64.74%           
  Complexity    19360    19360           
=========================================
  Files          1281     1281           
  Lines         75622    75622           
  Branches       1333     1333           
=========================================
  Hits          48959    48959           
  Misses        26271    26271           
  Partials        392      392           

Flag	Coverage Δ	Complexity Δ
#javascript	54.03% <ø> (ø)	0.00 <ø> (ø)
#phpunit	65.92% <100.00%> (ø)	19360.00 <0.00> (ø)

Impacted Files	Coverage Δ	Complexity Δ
...ilesharing/templates/settings-personal-general.php	100.00% <ø> (ø)	0.00 <0.00> (ø)
core/templates/layout.base.php	0.00% <ø> (ø)	0.00 <0.00> (ø)
core/templates/layout.guest.php	0.00% <ø> (ø)	0.00 <0.00> (ø)
core/templates/layout.user.php	0.00% <ø> (ø)	0.00 <0.00> (ø)
apps/dav/lib/HookManager.php	53.33% <100.00%> (ø)	17.00 <0.00> (ø)
lib/private/legacy/defaults.php	59.25% <100.00%> (ø)	45.00 <0.00> (ø)

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[ChrisEdS]

LGTM. Thank you for taking care.

[phil-davis]

Note: this PR goes into master. If the merge-back of the current release-10.5.0 branch happens ( #37648 ) then this will automatically end up in the new release-10.5.0 branch that gets started next week.

Otherwise this will need to be backport to release-10.5.0