### Improved devx of running many pallets simultaneously

Changes to /cmd:
- Replace (flip) `--continue-on-fail` with `--fail-fast`, but only for
`bench`. This makes all pallets/runtimes run non-stop by default, as it
was primary use-case during tests
- The list of successful/failed pallets was hard to find within tons of
logs, so decided to write only needed logs in a file, and output as a
summary in the workflow and in the comment
- Side fix: updated `tasks_example` to `pallet_example_tasks` to make
compliant with standard naming

<img width="1006" alt="image"
src="https://github.com/user-attachments/assets/14896041-7018-4a0d-92b7-4508e81913c2">

+ added command results to workflow summary:
<img width="1275" alt="image"
src="https://github.com/user-attachments/assets/b4a8afdb-dc9f-4ff9-9720-28a88956035f">

---------

Co-authored-by: GitHub Action <action@github.com>

Related to
https://github.com/paritytech/polkadot-sdk/pull/5924#issuecomment-2393558697

improve prdoc arguments validation & help:
- convert audiences options to snake_case. Fixes
https://github.com/paritytech/polkadot-sdk/issues/5927
  - support more than one audiences
  - define allowed bump options
- infer --pr from the actual PR (now it's optional, can still be
overwritten)


![image](https://github.com/user-attachments/assets/24e18fe2-2f67-4ce0-90e4-34f6c2f860c9)

Test evidence:
https://github.com/paritytech-stg/polkadot-sdk/pull/52/commits/6dd274e3678d287c163cfa6cb696acee9852767d

Fixes https://github.com/paritytech/polkadot-sdk/issues/5647

- [x]  create new command (reusing original py module)
- [x]  add unit-test cases (just the fact of proxy)
- [x]  update docs

Closes https://github.com/paritytech/product-engineering/issues/93

- Deprecates old command bot bash scripts. New cmd implementation is
re-written on Python
- Deprecates `sync` command, which was never used
- Benchmarks:
- Uses new
[frame-omni-bencher](https://crates.io/crates/frame-omni-bencher)
- Simplifies usage to only providing a runtime and/or pallet name (even
multiple runtimes or pallets)
- Supports sub-modules (like `/cmd bench --runtime dev --pallet
pallet_asset_conversion_ops`)
- Can regenerate all weights with one command (substrate, polkadot,
cumulus) for provided pallet(s) name
- Adds [subweight](https://crates.io/crates/subweight-core) diff as a
result of bench command