Address PR review comments

- Refactor targetPaths/findOwnPaths to class-based implementations with
  unified caching and .dir/.rootDir properties alongside resolve methods
- Replace jest.mock with jest.spyOn in plugin-manager.test.ts
- Remove paths compatibility wrapper from repo-tools, migrate all internal
  consumers to use targetPaths from @backstage/cli-common directly
- Fix changeset package name (@techdocs/cli not @backstage/techdocs-cli)
- Add migration examples to cli-common changeset
- Update API report for cli-common

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/cli-node/src/paths.ts

@@ -21,16 +21,16 @@ const ownPaths = findOwnPaths(__dirname);
 /* eslint-disable-next-line no-restricted-syntax */
 export const paths = {
   get ownDir() {
-    return ownPaths.resolve();
+    return ownPaths.dir;
   },
   get ownRoot() {
-    return ownPaths.resolveRoot();
+    return ownPaths.rootDir;
   },
   get targetDir() {
-    return targetPaths.resolve();
+    return targetPaths.dir;
   },
   get targetRoot() {
-    return targetPaths.resolveRoot();
+    return targetPaths.rootDir;
   },
   resolveOwn: ownPaths.resolve,
   resolveOwnRoot: ownPaths.resolveRoot,