docs: Updated documentation and Sphinx configuration (#1845)

# What does this PR do?

The goal of this PR is to make the pages easier to navigate by surfacing
the child pages on the navbar, updating some of the copy, moving some of
the files around.

Some changes:
1. Clarifying Titles
2. Restructuring "Distributions" more formally in its own page to be
consistent with Providers and adding some clarity to the child pages to
surface them and make them easier to navigate
3. Updated sphinx config to not collapse navigation by default
4. Updated copyright year to be calculated dynamically 
5. Moved `docs/source/distributions/index.md` ->
`docs/source/distributions/starting_llama_stack_server.md`

Another for https://github.com/meta-llama/llama-stack/issues/1815

## Test Plan
Tested locally and pages build (screen shots for example).

## Documentation
###  Before:
![Screenshot 2025-03-31 at 1 09
21 PM](https://github.com/user-attachments/assets/98e34f76-f0d9-4055-8e2c-441b1e7d8f6a)

### After:
![Screenshot 2025-03-31 at 1 08
52 PM](https://github.com/user-attachments/assets/dfb6b8ad-3a1d-46b6-8f54-0c553664093f)

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

docs/source/conf.py

@@ -16,6 +16,7 @@ from docutils import nodes
 from pathlib import Path
 import requests
 import json
+from datetime import datetime
 
 # Read version from pyproject.toml
 with Path(__file__).parent.parent.parent.joinpath("pyproject.toml").open("rb") as f:
@@ -28,7 +29,7 @@ with Path(__file__).parent.parent.parent.joinpath("pyproject.toml").open("rb") a
     llama_stack_version_link = f"<a href='{llama_stack_version_url}'>release notes</a>"
 
 project = "llama-stack"
-copyright = "2025, Meta"
+copyright = f"{datetime.now().year}, Meta"
 author = "Meta"
 
 # -- General configuration ---------------------------------------------------
@@ -104,6 +105,8 @@ source_suffix = {
 # html_theme = "alabaster"
 html_theme_options = {
     "canonical_url": "https://github.com/meta-llama/llama-stack",
+    'collapse_navigation': False,
+
     # "style_nav_header_background": "#c3c9d4",
 }