Address remaining gaps with the memory bounds design.

[tobz]

This issue is a high-level holding area for the various gaps that have been identified with the current memory bounds design, as well as the implementation/usage of memory bounds.

Non-exhaustive list of gaps, not necessarily in priority order:

• Memory usage when extending event buffers is attributed to components #185
• Override more defaults on the TLS client configuration when building HTTPS clients. #196
• Add support for expiration to the context resolver. #198