build: move e2e dependencies into e2e/go.mod

Several packages are only used while running the e2e suite. These
packages are less important to update, as the they can not influence the
final executable that is part of the Ceph-CSI container-image.

By moving these dependencies out of the main Ceph-CSI go.mod, it is
easier to identify if a reported CVE affects Ceph-CSI, or only the
testing (like most of the Kubernetes CVEs).

Signed-off-by: Niels de Vos <ndevos@ibm.com>

e2e/vendor/github.com/Microsoft/go-winio/internal/stringbuffer/wstring.go

@@ -0,0 +1,132 @@
+package stringbuffer
+
+import (
+	"sync"
+	"unicode/utf16"
+)
+
+// TODO: worth exporting and using in mkwinsyscall?
+
+// Uint16BufferSize is the buffer size in the pool, chosen somewhat arbitrarily to accommodate
+// large path strings:
+// MAX_PATH (260) + size of volume GUID prefix (49) + null terminator = 310.
+const MinWStringCap = 310
+
+// use *[]uint16 since []uint16 creates an extra allocation where the slice header
+// is copied to heap and then referenced via pointer in the interface header that sync.Pool
+// stores.
+var pathPool = sync.Pool{ // if go1.18+ adds Pool[T], use that to store []uint16 directly
+	New: func() interface{} {
+		b := make([]uint16, MinWStringCap)
+		return &b
+	},
+}
+
+func newBuffer() []uint16 { return *(pathPool.Get().(*[]uint16)) }
+
+// freeBuffer copies the slice header data, and puts a pointer to that in the pool.
+// This avoids taking a pointer to the slice header in WString, which can be set to nil.
+func freeBuffer(b []uint16) { pathPool.Put(&b) }
+
+// WString is a wide string buffer ([]uint16) meant for storing UTF-16 encoded strings
+// for interacting with Win32 APIs.
+// Sizes are specified as uint32 and not int.
+//
+// It is not thread safe.
+type WString struct {
+	// type-def allows casting to []uint16 directly, use struct to prevent that and allow adding fields in the future.
+
+	// raw buffer
+	b []uint16
+}
+
+// NewWString returns a [WString] allocated from a shared pool with an
+// initial capacity of at least [MinWStringCap].
+// Since the buffer may have been previously used, its contents are not guaranteed to be empty.
+//
+// The buffer should be freed via [WString.Free]
+func NewWString() *WString {
+	return &WString{
+		b: newBuffer(),
+	}
+}
+
+func (b *WString) Free() {
+	if b.empty() {
+		return
+	}
+	freeBuffer(b.b)
+	b.b = nil
+}
+
+// ResizeTo grows the buffer to at least c and returns the new capacity, freeing the
+// previous buffer back into pool.
+func (b *WString) ResizeTo(c uint32) uint32 {
+	// already sufficient (or n is 0)
+	if c <= b.Cap() {
+		return b.Cap()
+	}
+
+	if c <= MinWStringCap {
+		c = MinWStringCap
+	}
+	// allocate at-least double buffer size, as is done in [bytes.Buffer] and other places
+	if c <= 2*b.Cap() {
+		c = 2 * b.Cap()
+	}
+
+	b2 := make([]uint16, c)
+	if !b.empty() {
+		copy(b2, b.b)
+		freeBuffer(b.b)
+	}
+	b.b = b2
+	return c
+}
+
+// Buffer returns the underlying []uint16 buffer.
+func (b *WString) Buffer() []uint16 {
+	if b.empty() {
+		return nil
+	}
+	return b.b
+}
+
+// Pointer returns a pointer to the first uint16 in the buffer.
+// If the [WString.Free] has already been called, the pointer will be nil.
+func (b *WString) Pointer() *uint16 {
+	if b.empty() {
+		return nil
+	}
+	return &b.b[0]
+}
+
+// String returns the returns the UTF-8 encoding of the UTF-16 string in the buffer.
+//
+// It assumes that the data is null-terminated.
+func (b *WString) String() string {
+	// Using [windows.UTF16ToString] would require importing "golang.org/x/sys/windows"
+	// and would make this code Windows-only, which makes no sense.
+	// So copy UTF16ToString code into here.
+	// If other windows-specific code is added, switch to [windows.UTF16ToString]
+
+	s := b.b
+	for i, v := range s {
+		if v == 0 {
+			s = s[:i]
+			break
+		}
+	}
+	return string(utf16.Decode(s))
+}
+
+// Cap returns the underlying buffer capacity.
+func (b *WString) Cap() uint32 {
+	if b.empty() {
+		return 0
+	}
+	return b.cap()
+}
+
+func (b *WString) cap() uint32 { return uint32(cap(b.b)) }
+func (b *WString) empty() bool { return b == nil || b.cap() == 0 }