[code_review] Do not use new examples in the experimental environment

[suhaibmujahid]

Resolves #4995

[suhaibmujahid]

The evaluation results:

--------------------
Variant Name: exclude-new
--------------------
New Comments: 330
New Valid Comments: 44
New Invalid Comments: 94
New Unevaluated Comments: 191
--------------------
Old Comments: 273
Old Valid Comments: 83
Old Invalid Comments: 188
--------------------
Recalled comments: 52.74725274725275
Recalled valid comments: 53.01204819277109
Recalled invalid comments: 53.191489361702125
--------------------
Missed valid comments: 46.98795180722892
Missed invalid comments: 46.808510638297875

This can be compared to #4984 (comment). It seems that the results did not improve as much as was shown in the approved examples PR.

[Copilot]

Pull Request Overview

This PR removes the use of new examples in the experimental environment by adding an optional time filter for generated comment examples and issuing a warning when running in an experimental environment.

• Introduces a new attribute (must_range) to the QueryFilter for handling range queries.
• Adds an experimental environment flag that filters examples based on patch creation date and prints a warning.
• Updates several function signatures to accept an optional created_before parameter for filtering comment examples.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
bugbug/vectordb.py	Adds the must_range filter support in QueryFilter.
bugbug/tools/code_review.py	Introduces experimental environment handling and updates function signatures to include an optional created_before parameter.

[marco-c]

It's a pity the improvement is gone :(