…#1645)

…1643) (#1652)

* Enforce usage of Sementic_Versioning when printing Alire/Alr version

To ensure a consistent formatting whatever the version.
The version string is now private, only the semver type is visible.

* Enforce usage of Sementic_Versioning for index versions

In commands with options that admit arguments, like '--prefix' in
'alr install', is useful to provide an argument name in the command
help that gives a hint of the expected type.

For example, 'alr install -h' shows the message:
====
OPTIONS
   --prefix=ARG   Override installation prefix (default is ...)
====

When changed to:
====
OPTIONS
   --prefix=DIR   Override installation prefix (default is ...)
====

the 'DIR' name of the argument immediately says what is expected in this
option. In cases where this is not so obvious, it helps even more.
For example, in 'alr build -h':
====
OPTIONS
   --profiles=LIST     Comma-separated list of <crate>=<profile> values (see description)
   --stop-after=STAGE  Build stage after which to stop (see description)
====

is a quick remainder of what is expected in that options.

* Update msys2 installer

* Ensure msys2 from commit is tested

This is just a minor quality-of-life improvement for packaging. Note
that this also quotes the argument to echo so that if (somehow)
$ALIRE_OS were set to a malicious value, no harm could be done.

* Force creation of missing soft link

* More detailed test of softlink installation