chore: version bump (#766)

docs(SupportPolicy): Mark 1.x End-of-Support (#757)

chore: backport maintenance/doc changes and prepare release for v1.9.1 (

#731)

* Add CBMC CI configuration (#709)

This commit adds a configuration file for the "CBMC Proofs" CI check.
This is in preparation for adding some custom check-out steps later.

* Use private submodules before CI run (#711)

* chore: Use continuous-integration environment for private submodule access (#714)

Co-authored-by: Robin Salkeld <salkeldr@amazon.com>

* chore: Add support policy (#720)

* Upgrade CBMC proof tools: starter kit and Litani 1.10.0 (#722)

* Upgrade proof tool submodules

This commit advances Litani to release 1.10.0, and the starter kit to
the tip-of-tree. This brings the following improvements:

- Profiling
    - Litani measures the memory usage of the CBMC safety checking and
      coverage checking jobs
    - The dashboard includes box-and-whisker diagrams for memory use per
      proof
    - The dashboard includes a graph of how many parallel jobs are
      running over the whole run, making it easy to choose a CI machine
      with enough parallelism
    - It is now possible to designate particular proofs as "EXPENSIVE";
      Litani runs expensive proofs serially, ensuring that they do not
      over-consume resources like RAM.

- UI improvements
    - Each pipeline page includes a table of contents
    - Each pipeline page includes a dependency graph of the pipeline
    - Each job on the pipeline page has a hyperlink to that job
    - The terminal output is now less noisy

* Change cbmc-batch.yaml to cbmc-proof.txt

This makes the proof layout consistent with the starter kit, which will
allow us to use a generic run script in a future commit. Putting this
in commit by itself because the diff is huge and not worth reading (just
moving some files and changing two lines in the runscript).

* Symlink run-cbmc-proofs.py to starter kit

The run script is now a symbolic link into the starter kit submodule,
meaning that it will be updated whenever the starter kit is. This is
done iso that E-SDK doesn't carry custom modifications to the run script
unless necessary; previous commits have made the E-SDK proofs consistent
with the generic starter kit conventions.

* fix: Simplify / update build instructions. (#713)

Co-authored-by: June Blender <juneb@users.noreply.github.com>
Co-authored-by: Alex Chew <alex-chew@users.noreply.github.com>

* fix(proof_timeout): mark high-memory proofs expensive (#710)

* Removed OOM test, as OOM is no longer possible from aws allocators (#728)

* chore: pin newer aws-sdk-cpp in macOS CI builds (#729)

* chore: update version number and changelog for v1.9.1

* chore: update CBMC CI submodules

Co-authored-by: Kareem Khazem <karkhaz@amazon.com>
Co-authored-by: Robin Salkeld <salkeldr@amazon.com>
Co-authored-by: Ben Farley <47006790+farleyb-amazon@users.noreply.github.com>
Co-authored-by: lizroth <30636882+lizroth@users.noreply.github.com>
Co-authored-by: June Blender <juneb@users.noreply.github.com>
Co-authored-by: Justin Boswell <boswej@amazon.com>

chore: pin newer aws-sdk-cpp in macOS CI builds (#729)

chore: update version number and CHANGELOG for v2.3.1 (#724)

feat: AWS KMS multi-Region Key support (#715)

Added the new keyring KmsMrkAwareSymmetricKeyring that supports AWS KMS
multi-Region keys.
Added the helper MultiKeyringBuilder that composes multiple
KmsMrkAwareSymmetricKeyrings together to handle multiple CMKs.

See https://docs.aws.amazon.com/kms/latest/developerguide/multi-region-keys-overview.html
for more details about AWS KMS multi-Region Keys.
See https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/configure.html#config-mrks
for more details about how the AWS Encryption SDK interoperates
with AWS KMS multi-Region keys.

feat: Improvements to the message decryption process (#708)

See GHSA-r8cc-xhh9-rg65.

feat: Improvements to the message decryption process. (#707)

See <GHSA-r8cc-xhh9-rg65>.

Co-authored-by: Robin Salkeld <salkeldr@amazon.com>

chore: update CHANGELOG.md

chore: Update CHANGELOG.md