Energy density estimator tests near 100% fail rate

**Describe the bug**

Looking at the month long statistics for tests named *energydensity*, the fail rate is near 100%
https://cdash.qmcpack.org/testOverview.php?project=QMCPACK&begin=2025-04-01&end=2025-04-27&filtercount=1&showfilters=1&field1=testname&compare1=63&value1=energydensity

These tests are mostly for legacy where the code has not been intentionally changed in months. Possible explanations include unintentional breakage of the tests, of the underlying code, or perhaps the tests &/or code were simply not robust after the last time they were "fixed". We could also have h5py issues similar to https://github.com/QMCPACK/qmcpack/pull/3367 Most of the reported numerics are close to passing, so larger error bars could also be part of the solution.

**To Reproduce**

ctest -R energydensity , any recent version

**Expected behavior**

Test should pass; we should have confidence in energy density.

**System:**

Any

**Additional context**

Did not yet try to bisect failure or check historical PR discussions.

Note that sometimes the tests do pass e.g. https://cdash.qmcpack.org/testSummary.php?project=1&name=short-diamondC_1x1x1_pp-vmc-estimator-energydensity-cell-4-4-check&date=2025-04-25 has 3 of 18 runs passing in VMC.

The earliest cdash results we have are in the last week of February and the tests were failing then
https://cdash.qmcpack.org/testOverview.php?project=QMCPACK&begin=2025-02-23&end=2025-02-28&filtercount=1&showfilters=1&field1=testname&compare1=63&value1=energydensity