cmd/plugin_install: use semver to render version

When installing a plugin from a local binary, Packer builds the name of
the plugin from the results of the `describe' command.

Depending on how the plugin is built, the version reported may or may
not contain a leading `v', which was not taken into account beforehand
and the leading `v' was always injected in the path.

This caused plugins that report a leading `v' in their version to
be installed with two v's in their path, making them impossible to load.

Therefore to fix this issue, we count on the version library to print
out a version without the leading v, and we inject that in the resulting
path.

command/plugins_install.go

@@ -303,7 +303,7 @@ func (c *PluginsInstallCommand) InstallFromBinary(opts plugingetter.ListInstalla
 	outputPrefix := fmt.Sprintf(
 		"packer-plugin-%s_v%s_%s",
 		pluginIdentifier.Type,
-		desc.Version,
+		semver.String(),
 		desc.APIVersion,
 	)
 	binaryPath := filepath.Join(