Helper for ICU C functions that fill a resizable buffer (Bytes or UChars) and indicate required size via U_BUFFER_OVERFLOW_ERROR.

It handles the common pattern of calling a C function, checking for buffer overflow, resizing the buffer, and retrying.

Parameters:

• initial_size: The initial capacity of the buffer.
• buffer_type: The type of buffer to use (Bytes or UChars).
• &block: A block that performs the ICU C function call.
  • The block receives the buffer (Bytes or UChars) and a pointer to the UErrorCode (LibICU::UErrorCode*). The block can access the buffer's capacity via buffer.size.
  • The block must return the actual length (Int32) of the data written (or the required length if overflow occurred).

Returns:

• The resulting String converted from the buffer contents.

Raises:

• ICU::Error if the C function returns an ICU error other than U_BUFFER_OVERFLOW_ERROR.
• Any exception raised within the block (other than ICU::Error related to overflow).

Example Usage:

result_string = ICU.with_auto_resizing_buffer(64, ICU::UChars) do |buffer, status_ptr|
  LibICU.some_icu_function(..., buffer, buffer.size, status_ptr)
end