Move the introduction text from install_dashboard() to display_plugins_table()

[SergeyBiryukov]

install_dashboard() starts with this text for the Featured tab of Add Plugins screen:

Plugins extend and expand the functionality of WordPress. You may automatically install plugins from the WordPress Plugin Directory or upload a plugin in .zip format by clicking the button at the top of this page.

Some similar sentences are also found in the display_plugins_table() function:

• For the Recommended tab: "These suggestions are based on the plugins you and other users have installed".
• For the Beta Testing tab: "You are using a development version of WordPress. These feature plugins are also under development".

To have these introductions in a single place, the first one should be moved to display_plugins_table() as well for consistency.

Some history here: [9141], [30889], [36297].

[sabbir1991]

Created a patch

[kapilpaul]

@sabbir1991

Welcome to trac. Thanks for the patch.

@SergeyBiryukov I have tested this patch and it's working as expected.

[SergeyBiryukov]

Hi there, welcome back to WordPress Trac! Thanks for the patch, it looks good to me too.

[SergeyBiryukov]

In 52936:

Plugins: Move the introduction text from install_dashboard() to display_plugins_table().

This brings some consistency to how the introduction is displayed for the Beta Testing, Featured, and Recommended tabs of the Add Plugins screen.

This commit also reorders the switch cases for the text in the same order as they are displayed.

Follow-up to [9141], [30889], [36297].

Props sabbir1991, kapilpaul.
Fixes #55389.