Add exclude glob option

[zhuravel]

Summary

Add support for multiple exclude patterns via --tests-exclude-glob option to allow excluding specific test files from the split. This option can be specified multiple times to exclude multiple patterns, matching the behavior of the --tests-glob option.

Motivation

I'm migrating from CircleCI to GitHub Actions and needed exclude pattern support similar to other test splitting tools:

• Knapsack Pro supports KNAPSACK_PRO_TEST_FILE_EXCLUDE_PATTERN (docs)
• split_tests (Go implementation) supports --exclude-glob pattern (repo)

I prefer split-test over the Go alternative, but the missing exclude pattern support was a blocker for my migration.

Usage Example

# Single exclude pattern
split-test --tests-glob 'spec/**/*_spec.rb' --tests-exclude-glob 'spec/system/**/*_spec.rb'

# Multiple exclude patterns
split-test --tests-glob 'spec/**/*_spec.rb' \
--tests-exclude-glob 'spec/system/**/*_spec.rb' \
--tests-exclude-glob 'spec/integration/**/*_spec.rb'

Disclosure

⚠️ Full disclosure: This code was generated with AI assistance (Claude Code). I have no prior Rust experience, so I would greatly appreciate a thorough review to ensure the implementation follows Rust best practices and project conventions.

[mtsmfm]

Thank you for sharing your motivation, it makes sense!