The process of searching for authlib-injector.jar has been changed to:
1. use ~/.hmcl/authlib-injector.jar if present
2. use ./authlib-injector.jar if present
3. download if none of above is present
Instead of checking for updates when logging in, we now do it at startup.
We only check for updates if there is at least one authlib-injector
server configured.
This changed is expected to imporve launching speed.
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