mol-script: bond* => link*; make link tests "covalent" by default; wip link tests

src/mol-model/structure/query/context.ts

src/mol-model/structure/query/queries/filters.ts

src/mol-model/structure/query/queries/internal.ts

src/mol-model/structure/query/queries/modifiers.ts

src/mol-model/structure/structure/unit/rings/compute.ts

src/mol-script/language/symbol-table/structure-query.ts

src/mol-script/runtime/query/table.ts

src/mol-script/script/mol-script/examples.ts

src/mol-script/script/mol-script/symbols.ts