refactor(core): static-query schematic incorrectly handles multiple tsconfigs (#29133)

Currently when the static-query runs for a project with multiple TypeScript
configuration files (e.g. a usual CLI project), the migration incorrectly
applies the code transformation multiple times. This is because the migration
is currently based on the source file contents in the file system, while the
actual source file contents could have already changed in the devkit schematic
tree.

PR Close #29133

packages/core/schematics/test/static_queries_migration_spec.ts

@@ -710,5 +710,30 @@ describe('static-queries migration', () => {
       expect(tree.readContent('/index.ts'))
           .toContain(`@${queryType}('test', { static: true }) query2: any;`);
     });
+
+    it('should properly handle multiple tsconfig files', () => {
+      writeFile('/src/index.ts', `
+        import {Component, ${queryType}} from '@angular/core';
+                        
+        @Component({template: '<span #test></span>'})
+        export class MyComp {
+          private @${queryType}('test') query: any;
+        }
+      `);
+
+      writeFile('/src/tsconfig.json', JSON.stringify({
+        compilerOptions: {
+          lib: ['es2015'],
+        }
+      }));
+
+      // The migration runs for "/tsconfig.json" and "/src/tsconfig.json" which both
+      // contain the "src/index.ts" file. This test ensures that we don't incorrectly
+      // apply the code transformation multiple times with outdated offsets.
+      runMigration();
+
+      expect(tree.readContent('/src/index.ts'))
+          .toContain(`@${queryType}('test', { static: false }) query: any;`);
+    });
   }
 });