Don't store XElement outside of processing rounds. #5139

Job	Run time
Gradle build	13m 30s
Validate Dagger version	14s
Bazel build	3m 57s
Bazel tests	5m 45s
Artifact verification tests	11m 41s
Artifact Android emulator tests (API ${{ matrix.api-level }})	0s
Artifact Java local tests	3m 40s
Artifact Android local tests (AGP 8.1.1)	9m 59s
Build Hilt Gradle plugin against latest AGP version	0s
Test Hilt Gradle plugin	8m 28s
Clean up GitHub Action caches	7s
Publish snapshot	0s
	57m 21s

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