Fix PsrpOperator constructor validation to use provision checks inste…

[bujjibabukatta]

Summary

Part of the burn-down tracked in #70296.

PsrpOperator.__init__ validated command/powershell/cmdlet/arguments/parameters
using truthiness checks instead of is not None checks. Per the guidance in #70296,
"was this provided" checks are allowed to stay in __init__, but must use is not None
polarity rather than truthiness — so this is a fix in place, not a move to execute().

What was wrong

• command/powershell/cmdlet were collected into a set before being passed to
  exactly_one(). If two of them happened to render to the same string, the set would
  collapse them and validation would incorrectly pass.
• if arguments and ..., if parameters and ..., if cmdlet: treated an explicitly
  provided empty list/dict/string as "not provided", silently skipping validation.

Fix

Replaced truthiness checks with is not None checks, and pass fields to exactly_one()
directly instead of via a set. __init__ is now limited to this provision check plus
plain self.field = field assignments.

Testing

Added three regression tests in test_psrp.py covering: two duplicate field values,
an empty arguments list, and an empty parameters dict — all now correctly raise
ValueError.

Related: #70296

Was generative AI tooling used to co-author this PR?

• Yes - Claude

Generated-by: Claude following the guidelines

[shahar1]

Please note that it's a competitor PR of #70347 (you may keep this open, but I might end up merging the other - depending which provides the best match first)

[eladkal]

Why was this file modified?