[5.1] CLI: Renaming and improving output of core:update:check

[Hackwar]

Summary of Changes

The commands for core updates are not consistent right now. This is a first attempt at getting a system into these commands and improving the output. This PR renames the core:check-updates command to core:update:check (and adds an alias to keep it backwards compatible) and extends the output to display the current Joomla version and the update channel we are currently on.

An additional command core:update:set-channel will allow to set the update channel in the future.

Testing Instructions

1. call php cli/joomla.php
2. call php cli/joomla.php core:update:check
3. call php cli/joomla.php core:check-updates

Actual result BEFORE applying this Pull Request

to 1.: See the command listed as core:check-updates
to 2.: See the command fail
to 3.: See the title "Joomla updates" and the text "You already have the latest Joomla version..."

Expected result AFTER applying this Pull Request

to 1.: See the command listed as core:update:check and with an alias of core:check-updates
to 2.: See the command go through successfully with the title "Joomla Update Status" and the currently selected update channel and the current Joomla version in addition to the next available version.
to 3.: See the command to also work successfully, like in 2.

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

[dautrich]

I have tested this item ✅ successfully on fcc5429

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/42594.}

[viocassel]

I have tested this item ✅ successfully on fcc5429

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/42594.}

[richard67]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/42594.}

[Razzo1987]

Thanks!