Use angle_on_all_platforms.isolate in angle_end2end_tests.isolate.
Use angle_on_all_platforms.isolate in angle_end2end_tests.isolate.

This avoids duplication of this isolate's logic.

BUG=501604

Review URL: https://codereview.chromium.org/1233453009

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#338550}

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