Returning loadPatch value from JUCEPluginBase

[remaininlight]

The return value of Patch::loadPatch (https://github.com/cmajor-lang/cmajor/blob/main/include/cmajor/helpers/cmaj_Patch.h#L1914) is a boolean indicating whether the patch is playable or not

This return value would be useful for code using the JUCEPluginBase but is currently swallowed in JUCEPluginBase::loadPatch (https://github.com/cmajor-lang/cmajor/blob/main/include/cmajor/helpers/cmaj_JUCEPlugin.h#L117), which returns void

This PR forwards the value from the Patch out through the Plugin method