feat: modify istio version& add layotto_without_xds

[seeflood]

Signed-off-by: seeflood [email protected]

What this PR does:

• modify istio version in main.go
  
  I used to modify istio version with Makefile, but I reverted it because I want the makefile script decoupled with the code.
  For example, if the code doesn't import xDS related packages, makefile will get error when trying to modify the istio version.

• add layotto_without_xds for non-xDS users
  

Which issue(s) this PR fixes:

Fixes #

It's subtask of #471

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov]

Codecov Report

Merging #714 (de6fc6c) into main (f87a806) will not change coverage.
The diff coverage is n/a.

❗ Current head de6fc6c differs from pull request most recent head c2a0e21. Consider uploading reports for the commit c2a0e21 to get more accurate results

@@           Coverage Diff           @@
##             main     #714   +/-   ##
=======================================
  Coverage   60.89%   60.89%           
=======================================
  Files         122      122           
  Lines        6432     6432           
=======================================
  Hits         3917     3917           
  Misses       2133     2133           
  Partials      382      382           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f87a806...c2a0e21. Read the comment docs.