op2: read 584-byte PVT0 records as PARAM data and add RVMASS

[Shaisolaris]

Fixes #875.

Two problems reading NX PARAM data from an OP2:

1. _read_subtable_3_4 treats any 584-byte record as a table3 header. For PVT/PVT0/PVTS the table3 parser is _read_pvto_3, which raises, so an OP2 whose PARAM record happens to be 584 bytes long fails to read. This keeps the PARAM tables out of that check (PARAM_TABLES = {b'PVT', b'PVT0', b'PVTS'}), so the record goes to the table4 parser like any other PARAM record. I kept it to the PARAM tables rather than all of GEOM_TABLES to keep the change small.
2. PARAM,RVMASS,YES is a string PARAM that was missing from STR_PARAMS_1, so _read_pvto_4_helper asserts (word=b'RVMASS') and the PARAM block is skipped. This adds RVMASS to STR_PARAMS_1.

Testing: I added TestOP2Params to test_op2_unit_tests.py:

• test_pvt0_rvmass reads an RVMASS/AUTOSPC PARAM record. It fails on main with AssertionError: word=b'RVMASS' and passes with this change.
• test_pvt0_record_of_length_584 runs _read_subtable_3_4 on a 584-byte PVT0 record with the record reads stubbed. On main the record goes to the table3 parser; with this change it goes to the table4 parser.

Both pass. I could not complete a full run of test_op2_unit_tests.py or test_op2_bugfixes.py locally within my time limit, so I am relying on CI for the rest.

[codecov]

Codecov Report

❌ Patch coverage is 27.58621% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.17%. Comparing base (ad407d2) to head (7495e43).

Files with missing lines	Patch %	Lines
pyNastran/op2/test/test_op2_unit_tests.py	22.22%	21 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #880      +/-   ##
==========================================
- Coverage   76.18%   76.17%   -0.01%     
==========================================
  Files        1093     1093              
  Lines      358978   359006      +28     
  Branches    37051    37051              
==========================================
+ Hits       273470   273477       +7     
- Misses      75834    75855      +21     
  Partials     9674     9674              

Files with missing lines	Coverage Δ
pyNastran/op2/op2_interface/op2_reader.py	78.59% <100.00%> (+<0.01%)	⬆️
pyNastran/op2/op2_interface/op2_scalar.py	76.66% <ø> (ø)
pyNastran/op2/test/test_op2_unit_tests.py	93.93% <22.22%> (-0.88%)	⬇️

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[SteveDoyle2]

The tests were not run because a new class was created. They are not automatically discovered. New op2 test classes need to be added to pyNastran/op2/test/all_tests.py

[SteveDoyle2]

thanks! I appreciate the PR!