reactflow v11 migration and fixes for GitGraph

[nelsonni]

The GitGraph component relies on dagre for calculating layout for acyclic digraphs, and react-flow-renderer (renamed to reactflow for v11) for rendering the nodes and edges. The state of these graphs are managed outside of Redux using a custom React Hook called useGitGraph.

However, no graph is generated when selecting a branch from the Repository Map drop-down menu, with the root cause being a two-fold issue. The Branch models stored in Redux contained no commits due to a Regex pattern mismatch, and invalid Node objects were being created when a processed Edge contains an undefined endpoint.

This PR introduces validation checks for edges before they are added to the graph, and updates the Regex patterns for parsing git-log, git-rev-parse, and git-rev-list output to properly capture commits.

This PR resolves #988.

Changes:

This PR makes the following changes:

• Migrate react-flow-renderer v10 to reactflow v11
• Validate parent commit oid values prior to adding edges in a GitGraph
• Capture commit messages when processing git-log output
  *revParse return type expanded to Promise<string | undefined> to properly model when the git-rev-parse command returns { stdout: undefined, stderr: undefined }
• Remove redundant .git-flow CSS class since reactflow Theming allows for style props
• Mitigate warnings from the Serializability Middleware in Redux Toolkit by storing timestamps as string instead of DateTime objects in the store
• Apply border-radius CSS attributes to scrollbars in Card component content to fix display issues when a square scrollbar appears on a rounded corner of a card