hotfix: support all subscriptions api results endpoint query parameters

[asonnenschein]

Summary

Adds missing query parameters (created, updated, completed, item-datetime) to Subscriptions API results endpoints, aligning with the OpenAPI specification.

Changes

• Async Client (planet/clients/subscriptions.py): Added 4 query parameters to get_results() and get_results_csv() with comprehensive docstrings
• Sync Client (planet/sync/subscriptions.py): Updated to accept and forward new parameters
• CLI (planet/cli/subscriptions.py): Added --created, --updated, --completed, --item-datetime options to results command
• Documentation (docs/cli/cli-subscriptions.md): Added "Filtering Results" section with examples

All datetime parameters support RFC 3339 format with date-times, closed intervals, and open intervals.

Example Usage

Python:

pl.subscriptions.get_results(                                                                                                                                        
    subscription_id="...",                                                                                                                                           
    completed="2024-01-01T00:00:00Z/.."                                                                                                                             
)                                                                                                                                                                    
                                                                                                                                                                     
CLI:                                                                                                                                                                 
planet subscriptions results SUBSCRIPTION_ID \
    --completed 2024-01-01T00:00:00Z/..

[tbarsballe]

One issue noted inline, aside from that it appears to work well.
I did get some unhelpful error messages when I messed up the time interval syntax, but that's more an issue with the Subscriptions API itself, so out-of-scope here.

% planet subscriptions results 3ad50be0-05ea-4a1c-82cc-1e288211e627 --created 2026-03-07/..
Error: {"error":{"reason":"Unexpected error","details":[]}}