progress: move from an internal package to external

This commit makes the previously internal `progress` package an
external API. The is the result of the discussion in images
PR#1150 where we decided that the progress module is not a great
fit for the "images" library.

We want to share this code between bootc-image-builder and
image-builder-cli now. In the future we will also want to
use it in the `worker-executor` in `osbuild-composer` to
parse the stream data from `osbuild`.

We plan to merge bootc-image-builder and image-builder-cli
medium term so importing code from bootc-image-buider in
image-builder cli is not that stange.

When we (longer-term) use this code the `worker-executor`
we will need to think about this again and maybe put it
back into images. However this commit unblocks us without
making anything worse.

bib/pkg/progress/export_test.go

@@ -0,0 +1,27 @@
+package progress
+
+import (
+	"io"
+)
+
+type (
+	TerminalProgressBar = terminalProgressBar
+	DebugProgressBar    = debugProgressBar
+	VerboseProgressBar  = verboseProgressBar
+)
+
+func MockOsStderr(w io.Writer) (restore func()) {
+	saved := osStderr
+	osStderr = w
+	return func() {
+		osStderr = saved
+	}
+}
+
+func MockIsattyIsTerminal(fn func(uintptr) bool) (restore func()) {
+	saved := isattyIsTerminal
+	isattyIsTerminal = fn
+	return func() {
+		isattyIsTerminal = saved
+	}
+}