Add more progress bars to `DataLoader`

[gipert]

Also improve DataLoader.browse() signature and docstring.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.07 :tada:

Comparison is base (f4f1940) 48.42% compared to head (51eb68b) 48.49%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #497 +/- ## ========================================== + Coverage 48.42% 48.49% +0.07% ========================================== Files 104 104 Lines 12461 12479 +18 ========================================== + Hits 6034 6052 +18 Misses 6427 6427 ``` | [Impacted Files](https://app.codecov.io/gh/legend-exp/pygama/pull/497?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=legend-exp) | Coverage Δ | | |---|---|---| | [src/pygama/vis/waveform\_browser.py](https://app.codecov.io/gh/legend-exp/pygama/pull/497?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=legend-exp#diff-c3JjL3B5Z2FtYS92aXMvd2F2ZWZvcm1fYnJvd3Nlci5weQ==) | `71.03% <ø> (ø)` | | | [src/pygama/dsp/build\_dsp.py](https://app.codecov.io/gh/legend-exp/pygama/pull/497?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=legend-exp#diff-c3JjL3B5Z2FtYS9kc3AvYnVpbGRfZHNwLnB5) | `84.21% <100.00%> (ø)` | | | [src/pygama/flow/data\_loader.py](https://app.codecov.io/gh/legend-exp/pygama/pull/497?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=legend-exp#diff-c3JjL3B5Z2FtYS9mbG93L2RhdGFfbG9hZGVyLnB5) | `77.19% <100.00%> (+0.69%)` | :arrow_up: | | [src/pygama/raw/build\_raw.py](https://app.codecov.io/gh/legend-exp/pygama/pull/497?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=legend-exp#diff-c3JjL3B5Z2FtYS9yYXcvYnVpbGRfcmF3LnB5) | `90.66% <100.00%> (ø)` | |

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