Use correct attribute tag in NestHost and ModuleMainClass

[rootvector2]

NestHost and ModuleMainClass pass Const.ATTR_NEST_MEMBERS to the Attribute constructor, so a parsed attribute reports the wrong getTag(): a NestHost reports ATTR_NEST_MEMBERS (26) instead of ATTR_NEST_HOST (25), and a ModuleMainClass reports 26 instead of ATTR_MODULE_MAIN_CLASS (24). Attribute.readAttribute selects the right class by name, but the object then mislabels itself, so JavaClass.getAttribute(Const.ATTR_NEST_HOST) / getAttribute(Const.ATTR_MODULE_MAIN_CLASS) return null for a class that has those attributes, while getAttribute(Const.ATTR_NEST_MEMBERS) hands back a NestHost/ModuleMainClass that the unchecked cast type-confuses with NestMembers; Const.getAttributeName(getTag()) also prints both as NestMembers. found by checking each Attribute subclass tag against Const — every other subclass passes its own constant.

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[garydgregory]

TY @rootvector2 , merged 🚀