[IMP] Inventory: Bringing least packages current

[erjer-odoo]

While working on the removal strategies overview script, I realized that the documentation for "Least packages removal" was out of date. In this PR, I did the following:

• Added a section about enabling the removal strategy
• Added a subsection about storing products in packages before they can be used
• Added subsections on enabling the strategy on the location or product category
• Updated screenshots to be current
• Updated language to be current with 18.3 forward

All of this work makes the last of the removal strategies docs consistent with the other removal strategies docs.

This saas-18.3 PR can be FWP up to master.

[robodoo]

[erjer-odoo]

Hi @larm-odoo ! I'm finishing up work on the removal strategies docs. This update brings it current, as well as consistent with the other removal strategies docs that I worked on last week. When you get a moment, can you review and let me know what you think? Thank you!