[regexp] Remove exhaustive Script_Extensions tests

The upstream test suite for Unicode property escapes [1] is exhaustive
and is updated soon after every new release of the Unicode Standard.
It is then upstreamed into Test262.

This patch simplifies our own Script_Extensions tests and the script
used to generate them. Now, only a few code points are tested for each
Script_Extension. This avoids unnecessary friction every time ICU
is updated based on a new Unicode version.

[1] https://github.com/mathiasbynens/unicode-property-escapes-tests
[2] https://github.com/tc39/test262/tree/master/test/built-ins/RegExp/property-escapes

Bug: chromium:850334, v8:7825
Change-Id: I792d6848ef48b41ea5e9db18b777040d019822f3
Reviewed-on: https://chromium-review.googlesource.com/1112250Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54003}