24.5 updates

[thatstoasty]

• Removed __content_length_bytes from header structs.
• Updated header structs so that bytes attributes are consistently not null terminated.
• Added to_string method to convert List or Span of bytes to a String.
• Updated some functions that created a copies of lists to take ownership of the buffer they receive instead of making a copy.
• Remove arg types from send external_call due to stdlib bug? Or perhaps intended behavior