Extrema algorithms with repeated values

[K-ballo]

Extrema algorithms (min_element/max_element/minmax_element) have specific semantics in case of repeated values. The existing unit tests don't cover these, as they only use random_iota as the input range. In particular:

• min_element is required to return the first min value,
• max_element is required to return the first max value,
• minmax_element is required to return the first min value and the last max value.

Tests for these cases should be added, and the implementations adjusted as needed.

[ajaygaur01]

added a PR for min_element kindly check

[harith-hacky03]

@hkaiser @K-ballo Created PR for semantics check of these functions , Can you please verify it?