Add .String method for dyn.Pattern (#3234)

## Changes
This PR adds a String() method for dyn.Patterns that are the symmetric
counterpart to `dyn.MustPatternToString`.

## Why
It is used in https://github.com/databricks/cli/pull/3044/files

## Tests
Unit tests.

Author: shreyas-goenka

libs/dyn/pattern.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"slices"
+	"strings"
 )
 
 // Pattern represents a matcher for paths in a [Value] configuration tree.
@@ -12,6 +13,37 @@ import (
 // The reverse is not true; not every [Pattern] is a valid [Path], as patterns may contain wildcards.
 type Pattern []patternComponent
 
+func (p Pattern) String() string {
+	buf := strings.Builder{}
+	first := true
+
+	for _, c := range p {
+		switch c := c.(type) {
+		case anyKeyComponent:
+			if !first {
+				buf.WriteString(".")
+			}
+			buf.WriteString("*")
+		case anyIndexComponent:
+			buf.WriteString("[*]")
+		case pathComponent:
+			if c.isKey() {
+				if !first {
+					buf.WriteString(".")
+				}
+				buf.WriteString(c.Key())
+			} else {
+				buf.WriteString(fmt.Sprintf("[%d]", c.Index()))
+			}
+		default:
+			buf.WriteString("???")
+		}
+
+		first = false
+	}
+	return buf.String()
+}
+
 // A pattern component can visit a [Value] and recursively call into [visit] for matching elements.
 // Fixed components can match a single key or index, while wildcards can match any key or index.
 type patternComponent interface {

libs/dyn/pattern_test.go

@@ -8,6 +8,28 @@ import (
 	assert "github.com/databricks/cli/libs/dyn/dynassert"
 )
 
+func TestPatternString(t *testing.T) {
+	patterns := []string{
+		"foo.bar",
+		"foo.bar.baz",
+		"foo[1]",
+		"foo[*]",
+		"*[1].bar",
+		"foo.*.bar",
+		"foo[*].bar",
+		"",
+		"foo",
+		"[1]",
+		"[*]",
+		"*",
+	}
+
+	for _, p := range patterns {
+		pp := dyn.MustPatternFromString(p)
+		assert.Equal(t, p, pp.String())
+	}
+}
+
 func TestNewPattern(t *testing.T) {
 	pat := dyn.NewPattern(
 		dyn.Key("foo"),