fix: extproc is discarded with failOpen is enabled for wasm

[zhaohuabing]

fix #7886

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[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.79%. Comparing base (44676b8) to head (c5a9861).
⚠️ Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/gatewayapi/envoyextensionpolicy.go	93.75%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7956      +/-   ##
==========================================
+ Coverage   72.75%   72.79%   +0.03%     
==========================================
  Files         235      235              
  Lines       35380    35384       +4     
==========================================
+ Hits        25742    25758      +16     
+ Misses       7800     7791       -9     
+ Partials     1838     1835       -3     

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[zhaohuabing]

We need this empty field, internal/gatewayapi/envoyextensionpolicy.go uses nil to decide whether a policy should be overridden or not.

gateway/internal/gatewayapi/envoyextensionpolicy.go

Lines 534 to 536 in 09b6456

	if r.EnvoyExtensions != nil {
	continue
	}

[zirain]

/retest