feat: possibility to precise which config name to load when loading config from file

[aaalloc]

Closes #585

Proposed Changes

Possibility to precise which config name we want when loading from_config_file

Checklist

• [x] CHANGELOG.md updated
• [ ] Rebased/mergeable
• [x] A test has been added if appropriate
• [x] pytest tests completes successfully
• [ ] Commit messages are conventional
• [X] Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (77cac49) 90.30% compared to head (3577c58) 90.30%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #586 +/- ## ======================================= Coverage 90.30% 90.30% ======================================= Files 39 39 Lines 3455 3456 +1 ======================================= + Hits 3120 3121 +1 Misses 335 335 ``` | [Impacted Files](https://app.codecov.io/gh/influxdata/influxdb-client-python/pull/586?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=influxdata) | Coverage Δ | | |---|---|---| | [influxdb\_client/client/influxdb\_client.py](https://app.codecov.io/gh/influxdata/influxdb-client-python/pull/586?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=influxdata#diff-aW5mbHV4ZGJfY2xpZW50L2NsaWVudC9pbmZsdXhkYl9jbGllbnQucHk=) | `98.78% <ø> (ø)` | | | [influxdb\_client/client/influxdb\_client\_async.py](https://app.codecov.io/gh/influxdata/influxdb-client-python/pull/586?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=influxdata#diff-aW5mbHV4ZGJfY2xpZW50L2NsaWVudC9pbmZsdXhkYl9jbGllbnRfYXN5bmMucHk=) | `88.52% <ø> (ø)` | | | [influxdb\_client/client/\_base.py](https://app.codecov.io/gh/influxdata/influxdb-client-python/pull/586?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=influxdata#diff-aW5mbHV4ZGJfY2xpZW50L2NsaWVudC9fYmFzZS5weQ==) | `97.72% <100.00%> (+<0.01%)` | :arrow_up: |

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