src: check if --icu-data-dir= points to valid dir

Call uc_init() after u_setDataDirectory() to find out if the data
directory is actually valid.

This commit removes parallel/test-intl-no-icu-data, added in commit
46345b93 ("src: make --icu-data-dir= switch testable").  It no longer
works now that an invalid --icu-data-dir= argument is rejected.
Coverage is now provided by parallel/test-icu-data-dir.

Fixes: https://github.com/nodejs/node/issues/13043
Refs: https://github.com/nodejs/node-gyp/issues/1199


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Steven R Loomis <srloomis@us.ibm.com>