AES ECB mode support

[skmcgrail]

Issues:

Resolves #573

Description of changes:

• Adds support for ECB mode with pkcs7 padding
• Adds support for ECB mode with pkcs7 padding using the streaming interface
• Adds support for ECB mode without padding (requires input/output to be multiple of block length).

Call-outs:

• Streaming mode doesn't support ECB without padding as the EVP interface doesn't have a way to toggle off the behavior for this mode.

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

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.48269% with 32 lines in your changes missing coverage. Please review.

Project coverage is 92.69%. Comparing base (c358484) to head (dcb21a1). Report is 114 commits behind head on main.

Files with missing lines	Patch %	Lines
aws-lc-rs/src/cipher/aes.rs	92.40%	11 Missing and 7 partials :warning:
aws-lc-rs/src/cipher/streaming.rs	93.75%	2 Missing and 7 partials :warning:
aws-lc-rs/src/cipher.rs	94.18%	3 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #597 +/- ## ========================================== - Coverage 95.80% 92.69% -3.11% ========================================== Files 61 67 +6 Lines 8143 9772 +1629 Branches 0 9772 +9772 ========================================== + Hits 7801 9058 +1257 - Misses 342 429 +87 - Partials 0 285 +285 ```

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