Add 'Add to existing Row with column' action

[guigro]

Summary

• Adds a new event "Add to existing Row with column" that allows writing data to a specific column in an existing row
• Input format: ID,COLUMN,value1,value2,... (e.g., PLAYER_123,C,Score,150 writes "Score" in C and "150" in D)
• Supports multi-letter columns (AA, AB, DF, etc.)
• Creates a new row with values at the correct offset if the key is not found

Test plan

• yarn start compiles without errors
• Send event with existing ID → values written at specified column
• Send event with non-existing ID → new row created with values at correct column offset
• Test with multi-letter columns (AA, AB, etc.)

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