fix: Use correct offset in snapshot (#2217)

[mofojed]

• Was using row.offsetInSnapshot, which was a "protected" API and recently removed from the JS API
• API was removed in JS API refactoring: refactor: Rewrite JS API to share server implementation of Flight/Barrage deephaven-core#5890
• Instead just use the viewport offset and add the index of the row in the snapshot, which is there in both versions of the API
• New API does support row.index, but this way is compatible with both
• Updated unit tests
• Tested using a deephaven.ui.list_view:

from deephaven import time_table, ui
import datetime

initial_row_count = 200
column_types = time_table(
    "PT1S",
    start_time=datetime.datetime.now() - datetime.timedelta(seconds=initial_row_count),
).update(
    [
        "Id=new Integer(i)",
        "Display=new String(`Display `+i)",
    ]
)

@ui.component
def ui_list_view_table():
    value, set_value = ui.use_state([])

    lv = ui.list_view(
        column_types,
        aria_label="List View",
        on_change=set_value,
        selected_keys=value,
    )

    text = ui.text("Selection: " + ", ".join(map(str, value)))

    return ui.flex(
        lv,
        text,
        direction="column",
        margin=10,
        gap=10,
        width=500,
        # necessary to avoid overflowing container height
        min_height=0,
    )

lv_table = ui_list_view_table()

(cherry picked from commit a479d6c)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.66%. Comparing base (b0a8658) to head (e3b6184).

Additional details and impacted files

@@                Coverage Diff                @@
##           release/v0.85    #2318      +/-   ##
=================================================
- Coverage          46.66%   46.66%   -0.01%     
=================================================
  Files                685      685              
  Lines              38490    38488       -2     
  Branches            9587     9773     +186     
=================================================
- Hits               17961    17959       -2     
+ Misses             20519    20477      -42     
- Partials              10       52      +42     

Flag	Coverage Δ
unit	46.66% <100.00%> (-0.01%)	⬇️

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