RFC: Fine-grained Timeout Configuration (#816)

* add: boilerplate for new RFC

* update: "Configuring Timeouts" section

* add: unstructured thoughts on confusing terms

* update: Refine and organize the terms section

* Update design/src/rfcs/rfc0007_timeout_config.md

Co-authored-by: Russell Cohen <rcoh@amazon.com>

* update: terms section based on comments

* add: section on current structure of services
add: proposal for where to implement timeouts

* update: implementation checklist section

* update: refer to read timeout instead of write timeout

* Update design/src/rfcs/rfc0007_timeout_config.md

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update design/src/rfcs/rfc0007_timeout_config.md

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update design/src/rfcs/rfc0007_timeout_config.md

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update design/src/rfcs/rfc0007_timeout_config.md

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* fix: update opening summary
update: terminology section per John's suggestions
add: section demonstrating necessary changes to Client
update: implementation checklist

* update: implementation status/notes
remove: TODO
add: note about layers

Co-authored-by: Russell Cohen <rcoh@amazon.com>
Co-authored-by: John DiSanti <jdisanti@amazon.com>