feat: centralize GitHub API requests with auth and retry logic

[jaredfholgate]

Summary

Introduces a centralized Invoke-GitHubApiRequest function that consolidates all GitHub API calls with:

• Automatic authentication via GitHub CLI (gh auth token) when available, increasing API rate limits
• Configurable retry logic for transient HTTP errors (408, 429, 500, 502, 503, 504)
• Consistent error handling across all GitHub API interactions

Changes

New Function

• Invoke-GitHubApiRequest — Central function for all GitHub HTTP requests with auth header injection and retry support

Updated Functions

• Get-GithubRelease — Uses Invoke-GitHubApiRequest instead of Invoke-WebRequest for downloading release artifacts
• Get-GithubReleaseTag — Uses Invoke-GitHubApiRequest instead of Invoke-RestMethod with inline retry logic removed
• Get-HCLParserTool — Uses Invoke-GitHubApiRequest for downloading HCL parser binaries
• Test-NetworkConnectivity — Routes api.github.com connectivity check through Invoke-GitHubApiRequest
• New-ModuleSetup — Propagates maxRetryCount parameter; fixes isFirstRun → firstRun variable references
• New-FolderStructure — Accepts and passes through maxRetryCount parameter
• Deploy-Accelerator — Adds github_max_retry_count parameter (alias: gmrc, githubMaxRetryCount)

Tests

• Updated Test-NetworkConnectivity.Tests.ps1 to mock Invoke-GitHubApiRequest for the GitHub API endpoint