runtime(python): update rendering of Unicode named literals in syntax script

runtime(python): update rendering of Unicode named literals in syntax script

This change:

* enforces that the alias starts with a letter
* allows the other words in an alias to be separated by either a space
  or a hyphen, but not both or double separators
* allows only a letter after space, possibly followed by letters or
  digits
* allows both letters and digits after a hyphen

Tested with:

    a = '\N{Cyrillic Small Letter Zhe} is pronounced as zh in pleasure'
    b = '\N{NO-BREAK SPACE} is needed here'
    # ... other tests here
    r = '\N{HENTAIGANA LETTER E-1} is a Japanese hiragana letter archaic ye'
    s = '\N{CUNEIFORM SIGN NU11 TENU} is a correction alias'
    t = '\N{RECYCLING SYMBOL FOR TYPE-1 PLASTICS} base shape is a triangle'
    print(a)
    print(b)
    print(r)
    print(s)
    print(t)

The tests confirm the behavior and are selected from real Unicode
tables/aliases to check these combinations based on the specification.

fixes: #17323
closes: #17735

Signed-off-by: Christian Brabandt <cb@256bit.org>