python3: bump to version 3.8

python3: bump to version 3.8

This required a bit work to get working, compared to other versions. So,
some things have changed a bit more significantly.

Some highlights:
* there is no longer a pgen executable, seems this is now part of
  libpython; let's see what this means for us in the future
* blake2 hash (from OpenSSL) detection needs some fixing; will upstream
  added patch 002-fix-blake2-detection.patch
* removed all bpo patches; those should be fixed in upstream
* some needed to be manually re-applied as stuff changed:
  - 001-enable-zlib.patch  - file changed
  - 004-do-not-write-bytes-codes.patch  - file changed
  - 015-abort-on-failed-modules.patch - variable was renamed
    cross_compiling -> CROSS_COMPILING
* 017_lib2to3_fix_pyc_search.patch - the code changed, it does not seem to
     have the original problem with respect to file-extension, as there
     does not seem to be any special extension logic anymore there
* 006-remove-multi-arch-and-local-paths.patch - dropped patch; I can't
     remember the full-details of this issue; it was something with
     Debian/Ubuntu's multi-arch stuff; it was probably added maybe due to
     some overzealous (on my part) thingy caused by some weird reports,
     that I could never solve; let's have this patch dropped and see
* make package/python3/refresh to reduce fuzz for the rest

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>