vte3-gi test: add omit method

Vte.check_version? does not exist.
Instead of defines `omit_if_not_respond`.
vte3-gi test: include VteTestUtils
vte3-gi test: add rewrap_on_resize test

rewrap_on_resize has been provided since vte 0.36.
vte3-gi test: omit_if_not_respond can accept String and Symbol in second argument explicitly
vte3-gi test: use Symbol instead of String