[lldb][NFC] Make Stream's IndentLevel an unsigned integers.

We expect it to be always positive values and LLVM/Clang's IndentLevel
values are already unsigned integers, so we should do the same.

lldb/include/lldb/Utility/Stream.h

@@ -338,8 +338,8 @@ public:
   /// Get the current indentation level.
   ///
   /// \return
-  ///     The current indentation level as an integer.
-  int GetIndentLevel() const;
+  ///     The current indentation level.
+  unsigned GetIndentLevel() const;
 
   /// Indent the current line in the stream.
   ///
@@ -353,10 +353,10 @@ public:
   size_t Indent(llvm::StringRef s);
 
   /// Decrement the current indentation level.
-  void IndentLess(int amount = 2);
+  void IndentLess(unsigned amount = 2);
 
   /// Increment the current indentation level.
-  void IndentMore(int amount = 2);
+  void IndentMore(unsigned amount = 2);
 
   /// Output an offset value.
   ///
@@ -411,7 +411,7 @@ public:
   ///
   /// \param[in] level
   ///     The new indentation level.
-  void SetIndentLevel(int level);
+  void SetIndentLevel(unsigned level);
 
   /// Output a SLEB128 number to the stream.
   ///
@@ -442,7 +442,7 @@ protected:
   uint32_t m_addr_size; ///< Size of an address in bytes.
   lldb::ByteOrder
       m_byte_order;   ///< Byte order to use when encoding scalar types.
-  int m_indent_level; ///< Indention level.
+  unsigned m_indent_level;         ///< Indention level.
   std::size_t m_bytes_written = 0; ///< Number of bytes written so far.
 
   void _PutHex8(uint8_t uvalue, bool add_prefix);

lldb/source/Target/Target.cpp

@@ -3177,7 +3177,7 @@ void Target::StopHook::SetThreadSpecifier(ThreadSpec *specifier) {
 
 void Target::StopHook::GetDescription(Stream *s,
                                       lldb::DescriptionLevel level) const {
-  int indent_level = s->GetIndentLevel();
+  unsigned indent_level = s->GetIndentLevel();
 
   s->SetIndentLevel(indent_level + 2);
 

lldb/source/Utility/Stream.cpp

@@ -185,16 +185,18 @@ Stream &Stream::operator<<(int64_t sval) {
 }
 
 // Get the current indentation level
-int Stream::GetIndentLevel() const { return m_indent_level; }
+unsigned Stream::GetIndentLevel() const { return m_indent_level; }
 
 // Set the current indentation level
-void Stream::SetIndentLevel(int indent_level) { m_indent_level = indent_level; }
+void Stream::SetIndentLevel(unsigned indent_level) {
+  m_indent_level = indent_level;
+}
 
 // Increment the current indentation level
-void Stream::IndentMore(int amount) { m_indent_level += amount; }
+void Stream::IndentMore(unsigned amount) { m_indent_level += amount; }
 
 // Decrement the current indentation level
-void Stream::IndentLess(int amount) {
+void Stream::IndentLess(unsigned amount) {
   if (m_indent_level >= amount)
     m_indent_level -= amount;
   else