text: Title: Improve the Structure of the Metrics Table
  Body: ## 🚀 Feature
  
  <!-- A clear and concise description of the feature proposal -->
  
  Improve the structure of the metrics table by reorganizing the columns/groups.
  
  
  ### Motivation
  
  <!-- Please outline the motivation for the proposal. Is your feature request related to a problem? e.g., I'm always frustrated when [...]. If this is related to another GitHub issue, please link here too -->
  
  In the metrics explorer, the comparison of different metrics and runs is very difficult due to the grouping by metric. In the following, I illustrated an example with three runs and three metrics grouped by parameter a. `X` stands for some arbitrary value. The evaluation and comparison of the runs is very challenging. And here we actually have a very simple example with just a few runs/metrics.
  
  | Group | Run | Group Config | Metric | Value | | |  | Run Params  | | | Actions |
  | --- | --- | --- | --- |  --- | --- | --- | --- | --- |  --- | --- | --- | 
  |  | Name|  hparams.a | Name | Group Min | Mean | Group Max | ... |  hparams.b  |  hparams.c  | ... | 
  | Group 1 |  Mixed: 3 Values |  0|  loss |  X | X | X
  |  | Run A | 0 | loss |  | X | | | | | | S |
  |  | Run B |  0 | loss |  | X | | | | | | S |
  |  | Run C |  0 | loss |  | X | | | | | | S |
  | Group 2 |  Mixed: 3 Values |  0|  acc|  X | X | X
  |  | Run A | 0 | acc |  | X | | | | | | S |
  |  | Run B |  0 | acc |  | X | | | | | | S | 
  |  | Run C |  0 | acc |  | X | | | | | | S | 
  | Group 3 |  Mixed: 3 Values |  0|  val_loss |  X | X | X
  |  | Run A | 0 | val_loss |  | X | | | | | | S | 
  |  | Run B |  0 | val_loss |  | X | | | | | | S | 
  |  | Run C |  0 | val_loss |  | X | | | | | | S | 
  | Group 4 |  Mixed: 3 Values |  1|  loss |  X | X | X
  |  | Run D | 1 | loss |  | X | | | | | | S | 
  |  | Run E |  1 | loss |  | X | | | | | | S | 
  |  | Run F |  1 | loss |  | X | | | | | | S | 
  | Group 5 |  Mixed: 3 Values |  1|  acc|  X | X | X
  |  | Run D | 1 | acc|  | X | | | | | | S | 
  |  | Run E |  1 | acc|  | X | | | | | | S | 
  |  | Run F |  1 | acc|  | X | | | | | | S | 
  | Group 6 |  Mixed: 3 Values |  1|  val_loss |  X | X | X
  |  | Run D | 1 | val_loss |  | X | | | | | | S | 
  |  | Run E |  1 | val_loss |  | X | | | | | | S | 
  |  | Run F |  1 | val_loss |  | X | | | | | | S | 
  
  ### Pitch
  
  <!-- A clear and concise description of what you want to happen. -->
  
  The structure can be improved by showing the metrics as columns instead of as separate groups (similar to the runs explorer). 
  Here is an example with the same data as above:
  
  | Group | Run | Group Config | Metrics |  | | | Run Params  | | |  Actions |
  | --- | --- | --- | --- |  --- | --- | --- | --- | --- | --- | --- |
  |  | Name|  hparams.a | loss |acc | val_loss  |  ... |  hparams.b  |  hparams.c  | ...
  | Group 1 |  Mixed: 3 Values |  0|  X±X |  X±X |  X±X |
  |  | Run A | 0 | X |  X |   X |  | | | | S |
  |  | Run B |  0 | X|  X |   X |   | | | | S |
  |  | Run C |  0 | X|  X |   X |   | | | | S |
  | Group 2 |  Mixed: 3 Values |  1 |  X±X |  X±X |  X±X |
  |  | Run D | 1 | X |  X |   X |   | | | | S |
  |  | Run E |  1 | X|  X |   X |   | | | | S |
  |  | Run F |  1 | X|  X |   X |   | | | | S |
  
  In this way:
  - The table has become much smaller and clearer
  - Comparing different runs as well as different metrics is much easier
  - Scales better when the number of runs and metrics increases
  - The existing managing of the columns can be used
  - In the group column, an aggregated value can be shown (e.g. mean±std, mean (min - max), or just the mean. Possibly selectable)
  - `S` stands for show/hide. In this way, one could easily show/hide a run from all plots instead of changing all individually
  
  ### Alternatives
  
  <!-- A clear and concise description of any alternative solutions or features you've considered, if any. -->
  
  ### Additional context
  
  <!-- Add any other context or screenshots about the feature request here. -->