modified existing extrema algo tests

[sleepingeight]

Fixes #6627

Proposed Changes

• Added a new test utility random_repeat to generate vectors having repeated values.
• This utility is used to test the extrema algorithms, and I've verified that the existing implementations work properly.

Any background context you want to provide?

Used uniform_int_distribution to generate random numbers. Tests for container_algorithms can also be modified, but the tests need to be modified to not use sentinel (as we have duplicate values in our vector). I can update the tests if usage of sentinel can be removed in these tests.

Checklist

Not all points below apply to all pull requests.

• [ ] I have added a new feature and have added tests to go along with it.
• [ ] I have fixed a bug and have added a regression test.
• [x] I have added a test using random numbers; I have made sure it uses a seed, and that random numbers generated are valid inputs for the tests.

[StellarBot]

Can one of the admins verify this patch?

[codacy-production[bot]]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for dcf267d7868a0deab2e6f746ca5be8dad6553eea[^1]	:white_check_mark: ∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (dcf267d7868a0deab2e6f746ca5be8dad6553eea)	Report Missing	Report Missing	Report Missing
Head commit (c88e3ec67bc1b4c97c3451149f9a1dbeadb65d46)	193847	165033	85.14%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#6724)	0	0	∅ (not applicable)

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[^1]: Codacy didn't receive coverage data for the commit, or there was an error processing the received data. Check your integration for errors and validate that your coverage setup is correct.

[hkaiser]

• This utility is used to test the extrema algorithms, and I've verified that the existing implementations work properly.

I wouldn't like removing the tests realted to sentinels.