Remove title attributes: the Network Themes list table

[afercia]

See related #24766 and all the following tickets about title attributes.

All the title attributes on the links in the Network Themes list table basically repeat the same information already conveyed by the link text. I'd say to just remove them all. See screenshot:

For accessibility and consistency I'd suggest to add an aria-label attribute to expand the links text, as done for example in the Plugins list table, e.g.:

<a ... aria-label="Enable Intergalactic">Enable</a>

[afercia]

First pass. Would need some feedback because, as far as I see, the Themes list table is now used only in the main site and no more used in the network single sites so I guess this kind of checks for the row action links text is now pointless? Or maybe I'm missing something :)
( $this->is_site_themes ? __( 'Enable' ) : __( 'Network Enable' ) )

[afercia]

Refreshed patch. As @jeremyfelt pointed out, the check for $this->is_site_themes is still necessary when editing sites in the "Themes" tab. Thus, also the aria-label should provide a double text to be used for "Enable" or "Network Enable".
Also, uses $theme->display( 'Name' ) instead of $theme->get( 'Name' ).

Would appreciate a final review :)

[SergeyBiryukov]

One issue with ternary operators is that translator comment with only be parsed for the first string, but not for the second:

/* translators: %s: theme name */ 
sprintf( ( $this->is_site_themes ? __( 'Enable %s' ) : __( 'Network Enable %s' ) ), $theme->display( 'Name' ) )

35051.3.patch​ replaces string concatenation with add_query_arg() and sprintf(), which fixes the issue and makes these lines more readable.

[afercia]

Thanks @SergeyBiryukov definitely more readable and elegant :)

[afercia]

In 35924:

Accessibility: Remove title attributes from the Network Themes list table.

Title attributes in the "Themes" screen and in the "Edit Site" screen Themes tab
are now replaced with aria-label attributes. Also, replaces string
concatenation with add_query_arg() and sprintf() to allow translator
comments to be properly parsed and for better code readability.

Props SergeyBiryukov, afercia.
Fixes #35051.