@ret was not initialized when there was only one partial match.

Also, refactor the code to return all matching values.

Fixes: 3fd9bf9d7d9fc0290fd25f709b60a3a8f5c7e334

https://github.com/NetworkManager/NetworkManager/pull/123

Before:

  $ nmcli c modify Dukkha ipv4.ignore no
  Error: invalid property 'ignore': 'ignore' is ambiguous (ignore-auto-routes x (null)).

After:

  $ nmcli c modify Dukkha ipv4.ignore no
  Error: invalid property 'ignore': 'ignore' is ambiguous (ignore-auto-routes x ignore-auto-dns).

Use the same form everywhere: "TRANSLATORS" instead of "Translators".
The manual also seems to prefer the upper-case form [1].

  $ sed 's/\<Translators\>: /TRANSLATORS: /g' $(git grep -l Translators) -i

[1] https://www.gnu.org/software/gettext/manual/gettext.html

when input matched the heading of two allowed values the match was
reported as ambiguous without checking if there was a perfect match
following: fixed.

Example of a failing input:
const char **allowed = [ "ipv4, ipv6, ip" ];
const char *input = "ip";

"ip" was detected as ambiguous.

Add a new device state reason code for unsupported IP method. It is
returned, for example, when users select manual IP configuration for
WWAN connections:

 # nmcli connection mod Gsm ipv4.method manual ipv4.address 1.2.3.4/32
 # nmcli connection up Gsm
 Error: Connection activation failed: The selected IP method is not
 supported

compared to the old:

 Error: Connection activation failed: IP configuration could not be
 reserved (no available address, timeout, etc.)

Note that we could instead fail the connection validation if the
method is not supported by the connection type, but adding such
limitation now could make existing connections invalid.

https://bugzilla.redhat.com/show_bug.cgi?id=1459529

Makes sense in order for the user to know that they're actually typing
the password (edited just to illustrate the point, the actual output was
shamefully messy and perhaps needs fixing too):

  $ nmcli c up Wrathmosphere
  Passwords or encryption keys are required to access the wireless network 'Wrathmosphere'.
  Password (802-1x.password): *********

Having it in libnm doesn't make any sense and prevents using it for more
internal functionality.

Too bad nm_utils_wifi_strength_bars() is already a public API.
No problem -- replace it with a compatible yet dumber equivalent.

In most cases, it copies the entire strv needlessly.
We can do better.

Also, the max_tokens argument is handled wrongly (albeit
not used anywhere anymore).