[docs] Refresh package install instructions across the website. (#19393)

Assorted documentation updates following some recent release
infrastructure work and improvements to the
[`setup_venv.py`](https://github.com/iree-org/iree/blob/main/build_tools/pkgci/setup_venv.py)
script:

* Mention "development packages" next to "stable releases" and "nightly
pre-releases", per
https://github.com/iree-org/iree/pull/19362#discussion_r1871947915
![image](https://github.com/user-attachments/assets/25266060-cd70-4b7d-9dd7-4f79a53f572e)
* Could keep that scoped to one page... but duplicating it across pages
helps with discoverability. Definitely open to hearing more opinions on
this.
* Converted package names into links to pypi where applicable, like
[`iree-base-runtime`](https://pypi.org/project/iree-base-runtime/)
* Removed references to https://pypi.org/user/google-iree-pypi-deploy/.
That account is no longer a good reference for which projects are
relevant. We could use an [organization
account](https://docs.pypi.org/organization-accounts/) for a similar
purpose.
* Adjusted icons used in several places
    
    Before | After
    -- | --

![image](https://github.com/user-attachments/assets/27c5603e-94c0-4dee-b2c8-c4c1b7a1b3ab)
|
![image](https://github.com/user-attachments/assets/88f1e0d1-eecf-4b96-8098-d1a1040c213c)

* Misc proofreading and style tweaks