refactor(ivy): move ngcc into a higher level folder (#29092)

PR Close #29092

packages/compiler-cli/ngcc/README.md

@@ -0,0 +1,30 @@
+# Angular Compatibility Compiler (ngcc)
+
+This compiler will convert `node_modules` compiled with `ngc`, into `node_modules` which
+appear to have been compiled with `ngtsc`.
+
+This conversion will allow such "legacy" packages to be used by the Ivy rendering engine.
+
+## Building
+
+The project is built using Bazel:
+
+```bash
+yarn bazel build //packages/compiler-cli/ngcc
+```
+
+## Unit Testing
+
+The unit tests are built and run using Bazel:
+
+```bash
+yarn bazel test //packages/compiler-cli/ngcc/test
+```
+
+## Integration Testing
+
+There are tests that check the behavior of the overall executable:
+
+```bash
+yarn bazel test //packages/compiler-cli/ngcc/test:integration
+```