feat: added logic to fill invalid value with null, so the chart don't have broken lines

[SagarRajput-7]

Summary

Time series charts in SigNoz display disconnected/broken lines when encountering invalid data points such as +Inf, +Infinity, NaN, or other non-numeric values. This creates a poor visualization experience and makes it difficult for users to interpret the data.

Solution

This PR adds functionality to properly handle invalid plot values by replacing them with null values, which ensures chart lines remain connected. The implementation:

1. Adds two new utility functions in dataUtils.ts:

   • isInvalidPlotValue(): Checks for invalid values (null, undefined, NaN, Infinity, etc.)
   • normalizePlotValue(): Converts invalid values to null and string numbers to actual numbers

2. Updates fillMissingXAxisTimestamps() in getUplotChartData.ts to use the new normalization function

Benefits

• Improved chart visualisation with continuous lines instead of broken segments
• Better user experience when viewing time series data with occasional invalid values
• More consistent data representation across all chart types

Related Issues / PR's

• The time series chart doesn't show connected line there are +inf in b/w points #5662

Screenshots

Affected Areas and Manually Tested Areas

• Manually tested with datasets containing various invalid values including +Infinity, NaN, and undefined
• Verified chart rendering maintains line continuity across these invalid points
• Tested across different chart types and time ranges

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Important

Adds logic to replace invalid plot values with null to prevent broken chart lines, using new utility functions in dataUtils.ts.

• Behavior:
  • Introduces isInvalidPlotValue() and normalizePlotValue() in dataUtils.ts to handle invalid plot values by replacing them with null.
  • Updates fillMissingXAxisTimestamps() in getUplotChartData.ts to use normalizePlotValue() for value normalization.
• Functions:
  • isInvalidPlotValue(): Checks for null, undefined, NaN, Infinity, and string representations of these values.
  • normalizePlotValue(): Converts invalid values to null and string numbers to actual numbers.

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