[RFC] Move logger `v_num` information out of progress bar and into simple log statement

Nobody has claimed this yet.

## Proposed refactor

Remove `v_num` from the progress bar here:
https://github.com/PyTorchLightning/pytorch-lightning/blob/5da065e287b44e2c1fe4f7951003813ed45365c9/pytorch_lightning/callbacks/progress/base.py#L217-L223

And add a simple Python log statement at the start of training with the version number for each logger.

### Motivation

1. It is a bit unclear to me why we have the logger v_num on the progress bar - there is no direct relation between the two. Why not have this information in a simple log statement at the start of training, and leave more space in the progress bar for other information? As @carmocca put it, the progress bar is "prime real estate".

2. When we have multiple loggers, we have the strange behavior of concatenating the two version numbers (relic of LoggerCollection) and if the concatenated version numbers is longer than 4 digits we truncate it:
https://github.com/PyTorchLightning/pytorch-lightning/blob/5da065e287b44e2c1fe4f7951003813ed45365c9/pytorch_lightning/callbacks/progress/base.py#L220-L222

Instead, we can just have log statements like this at the start of training:
```
Initialized TensorBoardLogger with version X.
Initialized WandbLogger with version Y.
```

cc @justusschock @awaelchli @rohitgr7 @edward-io @borda @ananthsub @kamil-kaczmarek @Raalsky @Blaizzy @carmocca

Start with pytorch_lightning/callbacks/progress/base.py at the linked v_num handling, then trace where training begins and logger initialization occurs for TensorBoardLogger and WandbLogger. Remove the progress-bar version display and add one startup log statement per logger, with tests confirming multiple logger versions are reported separately.

Written by the indexing model from the issue text.