"Separate" tree-sitter parser list for indirect buffers

"Separate" tree-sitter parser list for indirect buffers

When create a parser for the indirect buffer, set the buffer field of
the parser to the indirect buffer, but add the parser to the base
buffer's parser list.  This way, all the parsers still get buffer
updates, but indirect buffer's parsers can have different narrowing than
the parsers of the base buffer.

When returning the parser list of a buffer, do filtering and only return
the parser for that buffer.

From user's POV, indirect buffers appear to have their own parser list.

* doc/lispref/parsing.texi (Using Parser): Remove the text describing
indirect buffer's special case.
* src/treesit.c (Ftreesit_parser_create): When create a parser for the
indirect buffer, set the buffer field of the parser to the indirect
buffer, but add the parser to the base buffer's parser list.
(Ftreesit_parser_list): Filter parser list, only return parsers for this
buffer.

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(cherry picked from commit e4cd26defc0e1a6deafbe4b2310ebdb3ffa4578f)