[Backport 2.x] Switch codecov uploads to use OIDC as tokenless is no-longer supported

[opensearch-trigger-bot[bot]]

Backport 4528640b4779580552fec35d9be9c670a19534b8 from #276

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 16.03%. Comparing base (ece879b) to head (7499903). Report is 8 commits behind head on 2.x.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 2.x #278 +/- ## ============================================= - Coverage 77.61% 16.03% -61.58% ============================================= Files 380 9210 +8830 Lines 62503 1438042 +1375539 ============================================= + Hits 48513 230639 +182126 - Misses 13990 1207403 +1193413 ``` | [Flag](https://app.codecov.io/gh/opensearch-project/opensearch-rs/pull/278/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opensearch-project) | Coverage Δ | | |---|---|---| | [integration](https://app.codecov.io/gh/opensearch-project/opensearch-rs/pull/278/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opensearch-project) | `30.38% <ø> (-47.24%)` | :arrow_down: | | [unit](https://app.codecov.io/gh/opensearch-project/opensearch-rs/pull/278/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opensearch-project) | `11.42% <ø> (?)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opensearch-project#carryforward-flags-in-the-pull-request-comment) to find out more.

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