fix: Correct nested groups for keepassxc builtin mode

[bakito]

This PR fixes nested groups for keepassxc when run in builtin mode and adds additional tests to assure the functionality.

[twpayne]

Looks great! One nit. If you don't want to fix it, I'll happily do it in a follow-up PR.

[twpayne]

nit: instead of passing lots of arguments with the same type, pass a struct with named fields. For an example, see

chezmoi/internal/chezmoi/sourcestate.go

Lines 340 to 366 in 94f00d1

	// AddOptions are options to SourceState.Add.
	type AddOptions struct {
	AutoTemplate bool // Automatically create templates, if possible.
	Create bool // Add create_ entries instead of normal entries.
	Encrypt bool // Encrypt files.
	EncryptedSuffix string // Suffix for encrypted files.
	Errorf func(string, ...any) // Function to print errors.
	Exact bool // Add the exact_ attribute to added directories.
	Filter *EntryTypeFilter // Entry type filter.
	OnIgnoreFunc func(RelPath) // Function to call when a target is ignored.
	PreAddFunc PreAddFunc // Function to be called before a source entry is added.
	ConfigFileAbsPath AbsPath // Path to config file.
	ProtectedAbsPaths []AbsPath // Paths that must not be added.
	RemoveDir RelPath // Directory to remove before adding.
	ReplaceFunc ReplaceFunc // Function to be called before a source entry is replaced.
	Template bool // Add the .tmpl attribute to added files.
	TemplateSymlinks bool // Add symlinks with targets in the source or home directories as templates.
	}
	// Add adds destAbsPathInfos to s.
	func (s *SourceState) Add(
	sourceSystem System,
	persistentState PersistentState,
	destSystem System,
	destAbsPathInfos map[AbsPath]fs.FileInfo,
	options *AddOptions,
	) error {

[bakito]

done

[twpayne]

Thank you!