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 ⚠️
aws-lc-rs/src/cipher/streaming.rs	93.75%	2 Missing and 7 partials ⚠️
aws-lc-rs/src/cipher.rs	94.18%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            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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[samuel40791765]

Suggested change

	// This is a sanity check hat should not fail. We validate in `decrypt` that in_out.len() % block_len == 0 for
	// This is a sanity check that should not fail. We validate in `decrypt` that in_out.len() % block_len == 0 for

[samuel40791765]

Seems like all of these using 2-9 (including the original code). What's the meaning behind the numbers and can we just move them within the macro/abstract them as variables?