Replace custom images with Themable Codicons

[JustinGrote]

Implements VSCode Themable Icons and Themable Colors mostly based on the newer Testing icons to produce a cleaner, more consistent and integrated visual look and feel, which can also be themed by theme authors accordingly.

Includes #450 as a dependency

Recording.2025-03-07.121526.mp4

Supporting changes:

1. Bump node/vscode/eslint/typescript to latest supported release to take advantage of latest API features
2. Add ts-pattern package for pattern matching of icon status to replace convoluted switch statements

[Copilot]

PR Overview

This PR replaces custom image-based icons with VSCode Themable Codicons to provide a cleaner, more consistent visual style that supports theming. Key changes include:

• Introducing new type definitions for VSCode theme icons and theme colors.
• Migrating existing icon lookup functions from custom images to a pattern‑matching based themable icon function.
• Updating all relevant tree view nodes to use the new themable icon API.

Reviewed Changes

File	Description
eslint.config.mjs	Added ESLint configuration utilizing the latest TS/JS linting settings
src/treeViews/shared/vscodeThemeIcon.ts	Introduces a union type for supported VSCode testing theme icons
src/treeViews/shared/vscodeThemeColor.ts	Introduces a union type for supported VSCode testing theme colors
src/treeViews/icons.ts	Migrates icon mapping to use ts‑pattern for themable icons
src/treeViews/shared/workflowRunNode.ts	Updates icon lookup to use the new themable icon function
src/treeViews/shared/attemptNode.ts	Updates icon lookup to use the new themable icon function
src/treeViews/shared/workflowJobNode.ts	Updates icon lookup to use the new themable icon function
src/treeViews/workflows/workflowStepNode.ts	Updates icon lookup to use the new themable icon function

Copilot reviewed 58 out of 58 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

src/treeViews/icons.ts:33

• [nitpick] The mapping for the 'cancelled' status reuses the theme color for skipped states. Consider reviewing if this is intentional or if a dedicated themable color should be used, and add a clarifying comment if necessary.

.with({status: "completed", conclusion: "cancelled"}, () => ["circle-slash", "testing.iconSkipped"])

[JustinGrote]

@AnthonyBorton please review, thanks :)