The current algorithm is like "collect all included files and subtract all excluded files".
Collecting all included and all excluded files relies on the file system. This can become slow
when the patterns used to exclude files resolve to a large number of files.

The new approach only collects all lintable files and checks them against the exclude patterns.
This can be done by in-memory string-regex-match and does therefore not require file system accesses.
The new implementation also no longer traverses directories that already match an exclude pattern.

(cherry picked from commit 152355e)

# Conflicts:
#	Source/SwiftLintFramework/Configuration/Configuration+LintableFiles.swift