Bump minimum version of param to 2.0 and add stream transform

[hoxbro]

• Bumps minimum version of param to 2.0
• Remove Panel Widget and replace with param.parameterized.resolve_ref did not work, because resolve_ref returns a list no matter what, and I only want the value parameter.
• Add Pipe and therefore Streams to reactive transform and therefore fixes #6229

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 91.66667% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 88.19%. Comparing base (d338915) to head (b76ee02).

Files	Patch %	Lines
holoviews/streams.py	85.71%	1 Missing :warning:
holoviews/util/__init__.py	75.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6230 +/- ## ======================================= Coverage 88.18% 88.19% ======================================= Files 321 321 Lines 67360 67344 -16 ======================================= - Hits 59402 59391 -11 + Misses 7958 7953 -5 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.