optimize: add default NoRoute and NoMethod handlers to assist troubleshooting

[DMwangnima]

What type of PR is this?

optimize

Check the PR title.

• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.
• Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. User docs repo

(Optional) Translate the PR title into Chinese.

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:
Users often do not proactively set 404/405 handlers via engine.NoRoute and engine.NoMethod, resulting in monitoring/logging being unable to obtain valid handler information through RequestContext.HandlerName.
Adding default NoRoute and NoMethod handlers provides valid handler information, enabling more effective troubleshooting.
zh(optional):
用户往往不会主动通过 engine.NoRoute 和 engine.NoMethod 设置 404/405 的 Handler，导致监控/打点通过 RequestContext.HandlerName 无法获取到有效的 Handler 信息。
添加默认的 NoRoute 和 NoMethod Handler 来提供有效的 Handler 信息，从而更好地排查问题。

(Optional) Which issue(s) this PR fixes:

(Optional) The PR that updates user documentation:

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.55%. Comparing base (150db78) to head (112c305).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/route/engine.go	75.00%	1 Missing and 1 partial ⚠️

❌ Your patch check has failed because the patch coverage (75.00%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1447      +/-   ##
==========================================
- Coverage   86.24%   85.55%   -0.69%     
==========================================
  Files         148      148              
  Lines       14158    14181      +23     
==========================================
- Hits        12210    12132      -78     
+ Misses       1417     1412       -5     
- Partials      531      637     +106     

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