rename "minimum_age" to "min_age" in ILM Phase Definitions

[talevy]

problem: There is inconsistency between the usage of min and max shorthands for
minimum and maximum. ILM's minimum_age for phase policy times adds to this inconsistency

solution: refactor minimum_age to be min_age

[elasticmachine]

Pinging @elastic/es-core-infra

[nishantraut]

Hi @talevy and Team,
I am new to this project, would like to start contribution, can you guide me. Thanks

[talevy]

hi @nishantraut, Although this issue would be a good first issue, I am going to work on this because we would like to get it in ASAP.

If you are interested in picking up other good first issues, we have a "good first issue" label where you can find other issues in ES that would be good starting points

issue list: https://github.com/elastic/elasticsearch/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22.

thank you for your interest in contributing! any help is very much appreciated!

[talevy]

closed in #35058