feat(plugins): open plugin API 1.2

API 1.1.0 shipped with 0.1.37 and its WIT is frozen in the released
snapshot, so additions now go into 1.2.0. The package version in wit/
and the SDK's copy, ENGINE_VERSION and both API_VERSION constants move to
1.2; the official plugins and test fixtures are rebuilt against it.

No interface, type or function changes: 1.0 and 1.1 components keep
linking. The release that ships 1.2 copies wit/ over
sdk/rust/openidea-plugin/tests/api/released/.

plugins/official/string-tools/dist/plugin.wasm.sources

@@ -1 +1 @@
-ac745c20866ed959252778116af068d7264187a53df64e2de090522b7ba5b722
+fa82a8596bd6505c769c0125ea26cef9af08535b36f650ddc4a353eb50866cea