fix: Eliminate compatibility risk of matching all domains for an MCP server

[CH3CHO]

Ⅰ. Describe what this PR did

Higress 2.1.8 doesn't support setting match_rule_domain to an empty string in mcp-session filter. So when generating mcp-session configs from annotations, always use wildcard for match-all to eliminate the compatibility risk.

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.95%. Comparing base (ef31e09) to head (132194a).
⚠️ Report is 734 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2973      +/-   ##
==========================================
+ Coverage   35.91%   44.95%   +9.04%     
==========================================
  Files          69       82      +13     
  Lines       11576    13378    +1802     
==========================================
+ Hits         4157     6014    +1857     
+ Misses       7104     7016      -88     
- Partials      315      348      +33     

Files with missing lines	Coverage Δ
pkg/ingress/kube/annotations/mcpserver.go	93.87% <100.00%> (ø)

... and 79 files with indirect coverage changes

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[johnlanni]

LGTM