[FilesList] Use the correct theming instance name from capabilities

[julien-nc]

...when setting the page title in the file list.

Theming capabilities do not include productName but name is there. See https://github.com/nextcloud/server/blob/master/apps/theming/lib/Capabilities.php#L96-L110

The page title is overridden by <NcAppContent> anyway. There is mistake there too. The Files page title is always like:
A directory - All files - Nextcloud - THEMING_NAME
and I think we want it to be
A directory - All files - THEMING_NAME
like it is defined in core/templates/layout.user.php, right?

I will create an issue in nextcloud-vue and link it here.

[skjnldsv]

Please use the app name for the commit message's scope :)
fix(files):

[susnux]

Alternative: #53339

Yes it should be the name.

[juliusknorr]

I think this is the logically more correct fix to use the instance name not product name, but would also merge #53339 in addition for cases where that is needed

[susnux]

/backport to stable31

[susnux]

/backport to stable30

[susnux]

/backport to stable30

[susnux]

/backport to stable29

[backportbot]

The backport to stable30 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable30
git pull origin stable30

# Create the new backport branch
git checkout -b backport/53321/stable30

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 01de909a 91ed3b2c

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/53321/stable30

Error: Failed to create pull request: Validation Failed: {"resource":"PullRequest","code":"custom","message":"A pull request already exists for nextcloud:backport/53321/stable30."} - https://docs.github.com/rest/pulls/pulls#create-a-pull-request

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[backportbot]

The backport to stable29 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable29
git pull origin stable29

# Create the new backport branch
git checkout -b backport/53321/stable29

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 01de909a 91ed3b2c

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/53321/stable29

Error: Failed to check for changes with origin/stable29: No changes found in backport branch

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.