Write documentation on the options and limitations of renaming/removing adapter codes

[muuki88]

Renaming or removing adapters is always painful and there's not enough guidance on what can and should be done.

Renaming pages

#6561 detected this feature

redirect_from:
	- /dev-docs/old-url

This allows to redirect for renamed pages.

[bretg]

We already have this FAQ entry https://docs.prebid.org/dev-docs/faq.html#im-a-developer---how-do-i-change-the-name-of-my-module

Sounds like we need to expand this a bit:

• cover the case of removing an alias
• help reviewers in PBJS, PBS, and docs teams understand and enforce

[muuki88]

Yeah, there are multiple cases missing

• removing an aliases
• changing an aliases
• remove a module
• rename a module (covered)
• mark module not available for versions (due to removal in major version an non-compliance)