In `ExpectFailure`, never generate "value of" lines based on bytecode.

The immediate motivation here is to prevent cl/801287069 and similar changes from affecting "value of" lines seen by users who are testing their own `Subject` implementations. But this is something that we've wanted before, including to make behavior consistent between the JVM (under which we can read bytecode) and other platforms (under which we can't/don't).

RELNOTES=Changed `ExpectFailure` to never generate "value of" lines based on bytecode. This slightly simplifies writing new tests with `ExpectFailure` and prevents future behavior changes in some `ExpectFailure` tests that already exist. However, it may also require changes to other existing `ExpectFailure` tests to remove or change any assertions about the "value of" line.
PiperOrigin-RevId: 802995279