Fix: Extract plugin name from error message with dot in plugin name

[pavog]

Problem
If a plugin has a dot in its name, the part after the . in the name is cut off. This is because this part is interpreted as a file extension and is not returned by

pathinfo($pluginPath, PATHINFO_FILENAME)

In the function extractPluginName(string $pluginPath): string we have to expeect that $pluginPath can be a path, a file name or a plugin name. Therefore, we must not simply cut it off after the .. Otherwise, for example, mclo.gs becomes just mclo, see this example: https://mclo.gs/4UEgJ73

Solution
We always extract the complete file name using

pathinfo($pluginPath, PATHINFO_BASENAME)

• If $pluginPath is a path, the file name (and extension) is extracted.
• If $pluginPath is the file name (and extension), nothing happens.
• If $pluginPath is only the plugin name, nothing happens.

We then check whether the result ends with .jar. We can assume that it does, because plugins must always be a .jar file. Other files are not loaded from the server.

[matthi4s]

I think the file name of the test should better reflect what's actually being tested, e.g. paper-plugin-with-dot-error-1-21.json