Fix bug #16265 with buffer caches when modifying text in indirect buffers.

Fix bug #16265 with buffer caches when modifying text in indirect buffers.

 src/search.c (newline_cache_on_off, find_newline): In indirect
 buffers, use the newline cache of the base buffer.
 src/insdel.c (invalidate_buffer_caches): If BUF is an indirect
 buffer, invalidate the caches of its base buffer.
 src/indent.c (width_run_cache_on_off, compute_motion): In indirect
 buffers, use the width-run cache of the base buffer.
 src/xdisp.c (redisplay_window): When the window displays an indirect
 buffer, and the character widths in the display table have
 changed, invalidate the width-run cache of the corresponding base
 buffer.
 src/fileio.c (Finsert_file_contents): When invalidating the newline
 cache, consider the case of inserting into indirect buffer.
 src/bidi.c (bidi_paragraph_cache_on_off, bidi_find_paragraph_start):
 In indirect buffers, use the paragraph cache of the base buffer.