fix(statistics): don't compute statistics when templates do not use them

[orhun]

Description

Do not compute statistics if they are not being used in the template.

Motivation and Context

might be related to #1519

How Has This Been Tested?

Locally.

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly (if applicable).
• I have formatted the code with rustfmt.
  • cargo +nightly fmt --all
• I checked the lints with clippy.
  • cargo clippy --tests --verbose -- -D warnings
• I have added tests to cover my changes.
• All new and existing tests passed.
  • cargo test

[codecov-commenter]

Codecov Report

❌ Patch coverage is 37.93103% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.25%. Comparing base (772e01d) to head (06d731c).

Files with missing lines	Patch %	Lines
git-cliff/src/lib.rs	0.00%	15 Missing ⚠️
git-cliff-core/src/config.rs	78.58%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1543      +/-   ##
==========================================
+ Coverage   48.65%   49.25%   +0.60%     
==========================================
  Files          26       26              
  Lines        2288     2305      +17     
==========================================
+ Hits         1113     1135      +22     
+ Misses       1175     1170       -5     

Flag	Coverage Δ
unit-tests	49.25% <37.94%> (+0.60%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.