rslog.CapturingLogger: Messages returns its underlying message slice

[aronatkins]

The capturing logger returns its underlying message slice, allowing a caller to modify the recorded message contents.

platform-lib/pkg/rslog/capturing_logger.go

Lines 129 to 131 in 8cb8e62

	func (l *CapturingLogger) Messages() []string {
	return l.hook.Messages()
	}

platform-lib/pkg/rslog/capturing_logger.go

Lines 143 to 148 in 8cb8e62

	func (h *captureMessageHook) Messages() []string {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return h.messages
	}

Messages() should return a copy of its message slice.

[aronatkins]

Related: Some callers want messages starting from a named offset, so they have code like:

messages := capLog.Messages()
selectedMessages := append([]string{}, messages[start:]...)

The capturing logger could include this functionality itself with MessagesFrom(start int). The result would be the selected subset of messages with no references to the underlying message slice.