Expose max_active_connections_override for client and meta request

[TingDaoK]

Issue #, if available:

aws-c-auth         v0.9.1 -> v0.9.2
aws-c-cal          v0.9.10 -> v0.9.11
aws-c-common       v0.12.5 -> v0.12.6
aws-c-http         v0.10.4 -> v0.10.7
aws-c-io           v0.23.1 -> v0.23.3
aws-c-s3           v0.9.2 -> v0.11.0
aws-lc             v1.61.4 -> v1.63.0
s2n                v1.5.27 -> v1.6.0

• Pick up the dynamic default part size from aws-c-s3.
• expose the max_active_connections_override for client and meta request.
• Now you can set memory limit via environment variable now.

Description of changes:

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.