[v2.9] Add "v26.1.x" option for "Docker Install URL" dropdown for RKE1

[chiukapoor]

Is your feature request related to a problem? Please describe.
As part of rancher/rancher#45439 we're adding support for Docker 26.1.x.

Describe the solution you'd like
UI dropdowns that allow picking "Docker Install URL" (e.g. on Node Template details page - not sure where else it may be referenced) should additionally have a "v26.1 (Recommended)" choice that populates https://releases.rancher.com/install-docker/26.1.sh when selected.

Describe alternatives you've considered
Note that the "Docker Install URL" is editable and doesn't limit users to only the available choices, so they can specify https://releases.rancher.com/install-docker/26.1.sh manually before this enhancement is done.
Consequently, the existing option "v26.0.x (Recommended)" should be changed to "v26.0.x".

Additional Information

When a new version of the docker install is published, the UI will fetch that version and mark it as the default. Our role usually involves adding the previous version to the hard-coded list to serve as a cache.

See rancher/ui#5045 and rancher/ui#5136 for examples of how this has been previously handled.

[chiukapoor]

@richard-cox backend related work is in progress, PR. This issue is not blocked on back-end anymore.

[nwmac]

@gaktive This got moved into the 2.9 milestone yesterday - FYI - will need to discuss.

[nwmac]

@chiukapoor Is the ask really to add v26.1 and keep v26.0 ?

We don't currently show more than one of a given major version, so I think we should be replacing v26.0 with v26.1 - can you confirm please.

[nwmac]

PR assuming a swap out: rancher/ui#5147

[mitulshah-suse]

@snasovich can you please comment on the this? Not sure if we have multiple minor versions till now.
#10996 (comment)

[IsaSih]

Tests pass on v2.9-16190ecee0aa3fb4aa570aa0fc932a36d9dcd082-head

[snasovich]

@chiukapoor Is the ask really to add v26.1 and keep v26.0 ?

We don't currently show more than one of a given major version, so I think we should be replacing v26.0 with v26.1 - can you confirm please.

@nwmac , is there a hard limitation to replace 26.0.x with 26.1.x?
FWIW we have precedent of having multiple minor versions with both v18.09.x and v18.06.x. Screenshot from 2.8-head:

TBH I'm not exactly sure why Docker started 26.1 while 26.0 was still pretty new but ideally I think we want our dropdown to mimic what is on https://docs.docker.com/engine/release-notes for non-ancient versions and they do list 26.0 separate from 26.1:

So if there are no hard limitations ideally we would like to have both 26.1 and 26.0 show up in the list with the latest (26.1) being the default.

Reopening this issue for visibility.

FYI @IsaSih @mitulshah-suse

[IsaSih]

2.9-head displays both versions. However, the default is 26.0, not 26.1. @snasovich if I understand it correctly, I believe that what you are requesting is already in place. Except by the default version, which could be addressed in a new issue.

[snasovich]

@IsaSih , I saw rancher/ui#5147 which replaced v26.0.x with v26.1.x and matched conversations in this issue. Not sure why both are displayed - there might have been a follow up PR.
I'm hoping we can change the default as part of this issue as it's essentially requested per the original issue's description.