[3.9] bpo-41076: Pre-feed the parser with the f-string expression location (GH-21054...

[3.9] bpo-41076: Pre-feed the parser with the f-string expression location (GH-21054) (GH-21190)

This commit changes the parsing of f-string expressions with the new parser. The parser gets pre-fed with the location of the expression itself (not the f-string, which was what we were doing before). This allows us to completely skip the shifting of the AST nodes after the parsing is completed..
(cherry picked from commit 1f0f4abb110b9fbade6175842b6a26ab0b8df6dd)