v3.42.34: Add spf13/afero for filesystem abstraction

- New internal/fs package for testable filesystem operations
- In-memory filesystem support for unit testing without disk I/O
- Swappable global FS: SetFS(afero.NewMemMapFs())
- Wrapper functions: ReadFile, WriteFile, Mkdir, Walk, Glob, etc.
- Testing helpers: WithMemFs(), SetupTestDir()
- Comprehensive test suite demonstrating usage
- Upgraded afero from v1.10.0 to v1.15.0

go.mod

@@ -97,6 +97,7 @@ require (
 	github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/schollz/progressbar/v3 v3.19.0 // indirect
+	github.com/spf13/afero v1.15.0 // indirect
 	github.com/spiffe/go-spiffe/v2 v2.5.0 // indirect
 	github.com/tklauser/go-sysconf v0.3.12 // indirect
 	github.com/tklauser/numcpus v0.6.1 // indirect