feat: add findings panel in gitguardian sidebar

[6d7a]

Context

Findings from ggshield scans are currently only surfaced in the Problems panel and inline as squiggles. There is no consolidated view of secrets detected across the open workspace.

What has been done

• add a "Findings" tree view in the GitGuardian sidebar, grouping detected secrets by file. Clicking a finding jumps to its location
• add a gitguardian.refreshFindings title-bar action to manually rebuild the list
• clear the diagnostic collection for a file when a re-scan finishes with no findings, so resolved secrets disappear from the editor and the new tree view
• export extractInfosFromMessage from the hover provider so the tree can reuse it to label findings by detector

Validation

• run the extension
• open a repository that contains an inline secret detected by ggshield
• ensure the new "Findings" view in the GitGuardian sidebar lists the file with a secret count, and that expanding it shows one entry per finding labelled with the detector
• click an entry and ensure the editor jumps to the matching range
• remove the secret from the file and save
• ensure the file disappears from the "Findings" view and the inline squiggle is cleared

PR check list

• As much as possible, the changes include tests
• If the changes affect the end user (new feature, behavior change, bug fix) then the PR has a changelog entry.