Move cremona db to features

[timokau]

This continues the work in #20382 and #25835.

To test this I ran ./sage -t --optional=sage,gap_packages,database_cremona_ellcurve $( git diff --name-only HEAD~2 ).

Next steps in getting rid of is_package_installed etc.:

• sage.doctest.control: Replace use of sage.misc.package.list_packages #30746 sage.doctest.control: Replace use of sage.misc.package.list_packages
• Deprecate sage.misc.package functions standard_packages, optional_packages, experimental_packages #30747 Deprecate all of sage.misc.package except for PackageNotFoundError

CC: @tscrim @kiwifb @mkoeppe

Component: build

Author: Timo Kaufmann, Jeroen Demeyer, Antonio Rojas

Branch/Commit: 9c2dcb5

Reviewer: Julian Rüth, Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/25825

[timokau]

comment:3

I just discovered #24718. This seems to be related/a duplicate. But that ticket seems to do some more unrelated stuff and probably needs a rebase. No clue why that is still "new".

[jdemeyer]

comment:4

In any case, I would rather have 1 ticket for each issue (1 for GAP, one for the Cremona database).

[timokau]

comment:5

Sure, I'll split it up.

[timokau]

New commits:

ca701d9

Replace gap package checks with features

[timokau]

Changed branch from u/gh-timokau/use-features to u/gh-timokau/cremona-db-features

[timokau]

Changed commit from c13f429 to ca701d9

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

1030350

Replace remona db checks with features

[sagetrac-git]

Changed commit from ca701d9 to 1030350

[timokau]

Description changed:

--- 
+++ 
@@ -1,4 +1,4 @@
-This continues the work in #20382. After this patch is applied, only one usage of `is_package_installed` remains: The one in `OptionalExtension`.
+This continues the work in #20382. After this patch and #25835 are applied, only one usage of `is_package_installed` remains: The one in `OptionalExtension` (#25828).
 
 To test this I ran `./sage -t --optional=sage,gap_packages,database_cremona_ellcurve $( git diff --name-only HEAD~2 )`.