Updates to Explorer docs (#5169)

## What are you changing in this pull request and why?

Updated the "Explore your dbt projects" page
https://docs.getdbt.com/docs/collaborate/explore-projects with these
changes:

Replaced `parent` and `child` with `upstream` and `downstream`,
respectively. This seems to be the winning nomenclature.

Changes to `Explore your project's lineage graph` section: 
- Replaced link to Loom with screenshot
- Updated selector search info. Leaning more on linked out pages for
detailed info
- Separated out selector search, graph operators, and set operations
- Used a toggle for the _interaction info_ 

Added new `Lenses` section.

Changes to `Search for resources` section:
- Replaced link to Loom with screenshot
- Renamed section to `Keyword search` 
- Removed `Search with selectors` section 
- Used toggles for search features and **Filters** side panel 

Changes to `Browse with the sidebar` section:
- Replaced link to Loom with screenshot
- Updated list 

Changes to `View resource details` section:
- Replaced link to Loom with screenshot
- Used toggles for all the "old example sections" 

### To-do for section titles 
- [x] For all title changes, locate and update URLs in source
- [x] Add redirects where applicable

## Checklist
- [x] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
so my content adheres to these guidelines.
- [x] For [docs
versioning](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#about-versioning),
review how to [version a whole
page](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
and [version a block of
content](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#versioning-blocks-of-content).
- [x] Needs review from product team