bpo-30455: Generate all token related code and docs from Grammar/Tokens. (GH-10370)

"Include/token.h", "Lib/token.py" (containing now some data moved from
"Lib/tokenize.py") and new files "Parser/token.c" (containing the code
moved from "Parser/tokenizer.c") and "Doc/library/token-list.inc" (included
in "Doc/library/token.rst") are now generated from "Grammar/Tokens" by
"Tools/scripts/generate_token.py". The script overwrites files only if
needed and can be used on the read-only sources tree.

"Lib/symbol.py" is now generated by "Tools/scripts/generate_symbol_py.py"
instead of been executable itself.

Added new make targets "regen-token" and "regen-symbol" which are now
dependencies of "regen-all".

The documentation contains now strings for operators and punctuation tokens.

Grammar/Tokens

@@ -0,0 +1,62 @@
+ENDMARKER
+NAME
+NUMBER
+STRING
+NEWLINE
+INDENT
+DEDENT
+
+LPAR                    '('
+RPAR                    ')'
+LSQB                    '['
+RSQB                    ']'
+COLON                   ':'
+COMMA                   ','
+SEMI                    ';'
+PLUS                    '+'
+MINUS                   '-'
+STAR                    '*'
+SLASH                   '/'
+VBAR                    '|'
+AMPER                   '&'
+LESS                    '<'
+GREATER                 '>'
+EQUAL                   '='
+DOT                     '.'
+PERCENT                 '%'
+LBRACE                  '{'
+RBRACE                  '}'
+EQEQUAL                 '=='
+NOTEQUAL                '!='
+LESSEQUAL               '<='
+GREATEREQUAL            '>='
+TILDE                   '~'
+CIRCUMFLEX              '^'
+LEFTSHIFT               '<<'
+RIGHTSHIFT              '>>'
+DOUBLESTAR              '**'
+PLUSEQUAL               '+='
+MINEQUAL                '-='
+STAREQUAL               '*='
+SLASHEQUAL              '/='
+PERCENTEQUAL            '%='
+AMPEREQUAL              '&='
+VBAREQUAL               '|='
+CIRCUMFLEXEQUAL         '^='
+LEFTSHIFTEQUAL          '<<='
+RIGHTSHIFTEQUAL         '>>='
+DOUBLESTAREQUAL         '**='
+DOUBLESLASH             '//'
+DOUBLESLASHEQUAL        '//='
+AT                      '@'
+ATEQUAL                 '@='
+RARROW                  '->'
+ELLIPSIS                '...'
+
+OP
+ERRORTOKEN
+
+# These aren't used by the C tokenizer but are needed for tokenize.py
+COMMENT
+NL
+ENCODING