Support NetBSD

[justsmth]

Issues:

Addresses: aws/aws-lc-rs#932

Description of changes:

Adds library support for NetBSD.

Call-outs:

• For aarch64 CPU feature detection, I adapted the logic I found here: https://github.com/NetBSD/src/blob/62c785e59d064070166dab5d2a4492055effba89/sys/arch/aarch64/aarch64/cpu.c#L363
• Both shared and static FIPS builds were failing for NetBSD.
• One (of the nine) OCSP "AmazonTrustServices" tests was failing -- the one that attempts connection to "ocsp.sectigo.com:80". The failure indicated No route to host. I suspect that it's attempting to connect via IPv6 and not finding appropriate routing for it. I disabled this test for NetBSD.

Testing:

Adds tests for both x86-64 and aarch64.

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.41%. Comparing base (d826708) to head (429ab7d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2754      +/-   ##
==========================================
- Coverage   78.42%   78.41%   -0.02%     
==========================================
  Files         683      683              
  Lines      116283   116283              
  Branches    16404    16405       +1     
==========================================
- Hits        91194    91182      -12     
- Misses      24213    24225      +12     
  Partials      876      876              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[MartinHusemann]

looks good to me