Put ingester disable chunk trimming a feature flag

[yeya24]

Signed-off-by: Ben Ye benye@amazon.com<!-- Thanks for sending a pull request! Before submitting:

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What this PR does:

This changes #6270 to mark the behavior optional under a feature flag.

We noticed that query result got changed if disabling chunk trimming for the following test case, captured by fuzz test.

https://github.com/cortexproject/cortex/actions/runs/11621920479/job/32367371250?pr=6298

The failure seems correctly captured as timestamp function returns timestamp of the sample so if certain samples are not trimmed then the result changes.

I think the behavior is not intended but let's make disable chunk trimming a feature flag for now and users can enable it at their own risk

query_fuzz_test.go:188: case 296 results mismatch.
        range query: timestamp({__name__="test_series_3"} @ end() offset 3m21s)
        res1: {job="test"} =>
        1730421141.171 @[1730419941.189]
        1730421141.171 @[1730419971.189]
        1730421141.171 @[1730420001.189]
        1730421141.171 @[1730420031.189]
        1730421141.171 @[1730420061.189]
        1730421141.171 @[1730420091.189]
        1730421141.171 @[1730420121.189]
        1730421141.171 @[1730420151.189]
        1730421141.171 @[1730420181.189]
        1730421141.171 @[1730420211.189]
        1730421141.171 @[1730420241.189]
        1730421141.171 @[1730420271.189]
        1730421141.171 @[1730420301.189]
        1730421141.171 @[1730420331.189]
        1730421141.171 @[1730420361.189]
        1730421141.171 @[1730420391.189]
        1730421141.171 @[1730420421.189]
        1730421141.171 @[1730420451.189]
        1730421141.171 @[1730420481.189]
        1730421141.171 @[1730420511.189]
        1730421141.171 @[1730420[54](https://github.com/cortexproject/cortex/actions/runs/11621920479/job/32367371250?pr=6298#step:10:55)1.189]
        1730421141.171 @[1730420571.189]
        1730421141.171 @[1730420601.189]
        1730421141.171 @[1730420631.189]
        1730421141.171 @[1730420661.189]
        1730421141.171 @[1730420691.189]
        1730421141.171 @[1730420721.189]
        1730421141.171 @[1730420751.189]
        1730421141.171 @[1730420781.189]
        1730421141.171 @[1730420811.189]
        1730421141.171 @[1730420841.189]
        1730421141.171 @[1730420871.189]
        1730421141.171 @[1730420901.189]
        1730421141.171 @[1730420931.189]
        1730421141.171 @[1730420961.189]
        1730421141.171 @[1730420991.189]
        1730421141.171 @[1730421021.189]
        1730421141.171 @[1730421051.189]
        1730421141.171 @[1730421081.189]
        1730421141.171 @[1730421111.189]
        1730421141.171 @[1730421141.189]
        res2: {job="test"} =>
        1730420931.171 @[1730419941.189]
        1730420931.171 @[1730419971.189]
        1730420931.171 @[1730420001.189]
        1730420931.171 @[1730420031.189]
        1730420931.171 @[1730420061.189]
        1730420931.171 @[1730420091.189]
        1730420931.171 @[1730420121.189]
        1730420931.171 @[1730420151.189]
        1730420931.171 @[1730420181.189]
        1730420931.171 @[1730420211.189]
        1730420931.171 @[1730420241.189]
        1730420931.171 @[1730420271.189]
        1730420931.171 @[1730420301.189]
        1730420931.171 @[1730420331.189]
        1730420931.171 @[1730420361.189]
        1730420931.171 @[1730420391.189]
        1730420931.171 @[1730420421.189]
        1730420931.171 @[1730420451.189]
        1730420931.171 @[1730420481.189]
        1730420931.171 @[1730420511.189]
        1730420931.171 @[1730420541.189]
        1730420931.171 @[1730420[57](https://github.com/cortexproject/cortex/actions/runs/11621920479/job/32367371250?pr=6298#step:10:58)1.189]
        1730420931.171 @[1730420601.189]
        1730420931.171 @[1730420631.189]
        1730420931.171 @[1730420661.189]
        1730420931.171 @[1730420691.189]
        1730420931.171 @[1730420721.189]
        1730420931.171 @[1730420751.189]
        1730420931.171 @[1730420781.189]
        1730420931.171 @[1730420811.189]
        1730420931.171 @[1730420841.189]
        1730420931.171 @[1730420871.189]
        1730420931.171 @[1730420901.189]
        1730420931.171 @[1730420931.189]
        1730420931.171 @[17304209[61](https://github.com/cortexproject/cortex/actions/runs/11621920479/job/32367371250?pr=6298#step:10:62).189]
        1730420931.171 @[1730420991.189]
        1730420931.171 @[1730421021.189]
        1730420931.171 @[1730421051.189]
        1730420931.171 @[1730421081.189]
        1730420931.171 @[1730421111.189]
        1730420931.171 @[1730421141.189]
    query_fuzz_test.go:193: 
        	Error Trace:	/home/runner/work/cortex/cortex/integration/query_fuzz_test.go:193
        	Error:      	finished query fuzzing tests
        	Test:       	TestDisableChunkTrimmingFuzz
        	Messages:   	1 test cases failed

Which issue(s) this PR fixes:
Fixes #

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[yeya24]

We on purposely ignore timestamp to reduce flakiness as it is a know imcompatible behavior

[alanprot]

Thanks