install istioctl in tmp dir when running E2E tests

[YaoZengzeng]

What type of PR is this?

/kind enhancement

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes part of #930

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.16%. Comparing base (d119669) to head (d4f1a84).
Report is 19 commits behind head on main.

see 74 files with indirect coverage changes

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[LiZhenCheng9527]

/lgtm

[kmesh-bot]

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