Add utility functions and types used for implementing the timeline header component

[kyasbal]

This PR adds utility classes or functions to implement the timeline header component.

• human-friendly-tick.ts calculates the minimum scale suitable for the current scale.
• HistogramCache is the utility to efficiently re-calculate the histogram because user's scroll may need to recalculate buckets in histograms.

[gemini-code-assist]

Summary of Changes

Hello @kyasbal, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the timeline component by introducing robust utilities for displaying time rulers and optimizing histogram data rendering. It includes new logic for determining human-friendly time intervals and a caching mechanism for log histograms, alongside a refactoring of rendering-related utility files to a more generalized canvas structure. These changes aim to improve the accuracy, performance, and maintainability of the timeline visualization.

Highlights

• Timeline Ruler Utilities: New utilities (human-friendly-tick.ts) are introduced to calculate and format human-friendly time ticks for the timeline ruler, supporting various zoom levels from milliseconds to days. This includes functions for time formatting and determining appropriate tick intervals based on zoom.
• Histogram Data Caching: A HistogramCache class is added to efficiently calculate and retrieve log histogram data. This optimization improves performance for timeline visualizations by using pre-calculated cumulative sums of log counts for different severities, allowing for O(1) retrieval of log counts within any time window.
• Rendering Component Refactoring: Several rendering-related utility files previously located in a gl directory (e.g., convertutil, glcontextmanager, rendering-loop-manager) have been renamed and moved to a more generalized canvas directory. This indicates a refactoring or generalization of the timeline's rendering components.

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[gemini-code-assist]

Code Review

This pull request introduces new utilities for the timeline ruler, including human-friendly-tick for calculating tick steps and a HistogramCache for optimizing histogram data retrieval. The changes also include refactoring by moving several files from a gl directory to a more general canvas directory.

The new utilities are well-designed and include corresponding unit tests. My review focuses on improving the clarity and robustness of the new code. Specifically, I've suggested simplifications in human-friendly-tick.ts and histogram-cache.ts.

One structural point to consider is the relocation of glcontextmanager.ts. While other files moved to the canvas directory are generic, this file remains specific to WebGL, which might be an inconsistent placement.

[kyasbal]

Blocker #456