fix: remove all eager len calls

[ikrommyd]

This PR aims to remove all eager len calls from coffea to adapt to the changes proposed in dask-contrib/dask-awkward#416

[ikrommyd]

analysis_tools tests are passing locally now that dask-contrib/dask-awkward#417 is merged

[ikrommyd]

@lgray I've searched the coffea src code and all len calls look fine to me. I'm not 100% sure about some in nanoevents and in the lookup tools. Please control-F it to cross-check if you have a little bit of time. Tests should be passing once dask-contrib/dask-awkward#417 is into a pypi release as they are passing locally. I'm not checking these though:

SKIPPED [2] tests/processor/servicex/__init__.py:30: could not import 'servicex': No module named 'servicex'
SKIPPED [1] tests/test_ml_tools.py:75: could not import 'tritonclient': No module named 'tritonclient'
SKIPPED [1] tests/test_ml_tools.py:122: could not import 'torch': No module named 'torch'
SKIPPED [1] tests/test_ml_tools.py:160: could not import 'xgboost': No module named 'xgboost'
SKIPPED [1] tests/test_parsl.py:10: could not import 'parsl': No module named 'parsl'
SKIPPED [1] tests/test_parsl.py:39: could not import 'parsl': No module named 'parsl'
SKIPPED [1] tests/test_parsl.py:126: could not import 'parsl': No module named 'parsl'
SKIPPED [1] tests/test_parsl.py:134: could not import 'parsl': No module named 'parsl'
SKIPPED [1] tests/test_spark.py:5: could not import 'pyspark': No module named 'pyspark'
SKIPPED [1] tests/test_spark.py:13: pyspark executor work currently in progress
SKIPPED [1] tests/test_spark.py:109: could not import 'pyspark': No module named 'pyspark'