refactor: update the schema link for copilot extensions

[huimiu]

Change the schema URL to the following link:

• Declarative Copilot: https://aka.ms/json-schemas/copilot/declarative-agent/v1.0/schema.json
• Plugin: https://aka.ms/json-schemas/copilot/plugin/v2.1/schema.json

Involving the following templates:

• API Plugin from scratch (None auth, API Key, AAD, OAuth).
• API Plugin from existing API.
• Basic Declarative Copilot.
• Declarative Copilot with a plugin (None auth, API Key, AAD, OAuth).
• Declarative Copilot with a plugin from existing API.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.61%. Comparing base (e396e30) to head (4e6155c).
Report is 2 commits behind head on release/5.10.0.

Additional details and impacted files

@@               Coverage Diff               @@
##           release/5.10.0   #12387   +/-   ##
===============================================
  Coverage           94.61%   94.61%           
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  Files                 582      582           
  Lines               34494    34494           
  Branches             6752     6835   +83     
===============================================
  Hits                32638    32638           
  Misses               1582     1582           
  Partials              274      274           

Files with missing lines	Coverage Δ
packages/spec-parser/src/constants.ts	100.00% <ø> (ø)