Implement exclude patterns from workspace settings

[0xnmn]

Re-implementing PR: https://github.com/sourcegraph/cody/pull/8037

This introduces the ability to exclude files from Cody's context based on the files.exclude, search.exclude, and .gitignore / .sourcegraph/.ignore .cody/ignore files located in the codebase root directory settings in VS Code.

The ContextFiltersProvider now utilizes these settings to determine if a file should be ignored. This is achieved by:

• Adding minimatch as a dependency to perform pattern matching.
• Introducing a static excludePatternGetter to fetch the exclude patterns and workspace folder.
• Implementing isExcludedByPatterns to check if a file path matches any of the exclude patterns.
• Adding ContextFiltersProviderError.ExcludePatternMatch to indicate when a file is excluded by the patterns.

This enhancement ensures that Cody respects the user's VS Code settings for excluding files, preventing irrelevant files from being included in the context.

Note: .sourcegraph/.ignore instead of .codyignore so that the same file can be used across sourcegraph products and not just cody

Test plan

• Try to open a file that is listed in the .gitignore / .sourcegraph/.ignore file at the root of the repo
• Confirm you can see the file being ignored tooltip when hovered over the cody icon at the bottom menu bar