fillData sorted data assumption fixed

[Dharmesh-Kota]

Description

This PR fixes a critical bug in the fillData helper in victory-stack, which incorrectly assumes that datasets passed into it are already sorted by _x. In many real-world cases, including the one demonstrated in Issue #3061, data may be unsorted. The previous implementation relied on array index alignment (index - indexOffset), which fails when data is unordered, leading to incorrect mapping of data points and insertion of unnecessary synthetic values.

Key Improvements:

• Introduced a Map-based lookup (dataMap) for _x values instead of index tracking.
• Ensured that missing values are correctly inserted when not present, even if input datasets are unsorted.
• Removed reliance on the assumption that data is sorted ahead of time.
• The updated implementation uses a Map for constant-time (O(1)) lookup of original data values by _x and avoids unnecessary scanning or mismatched indexing logic

Results in more predictable and performant iteration, especially with larger or unsorted datasets

Fixes # (issue)

Type of Change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Locally tested with real-world datasets containing unsorted _x values.
• Validated by comparing results of fillData before and after the patch using sample datasets.
• Ensured correct reconstruction of series with missing x-values using patched logic.

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Latest commit: 8a2ca37

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