Fixed Key Record support based on TLS client certificates

[folkertdev]

No description provided.

[codecov]

Codecov Report

Attention: 17 lines in your changes are missing coverage. Please review.

Comparison is base (97c731c) 83.65% compared to head (cc058e1) 83.81%.

Files	Patch %	Lines
ntp-proto/src/nts_record.rs	92.77%	12 Missing ⚠️
ntpd/src/daemon/keyexchange.rs	90.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1196      +/-   ##
==========================================
+ Coverage   83.65%   83.81%   +0.16%     
==========================================
  Files          63       63              
  Lines       17457    17669     +212     
==========================================
+ Hits        14604    14810     +206     
- Misses       2853     2859       +6     

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[squell]

There is a bit of churn in some of the commits as test-cases were added and then removed; so I'd recommend squashing this. This PR adds:

• FixedKeyRequests (scaffolding already present in main)
• support in the configuration for adding NTS pool server certificates to the NtsKe configuration (authorized-pool-server-certificates = [ "file.pem", "file2.pem", ...]). I'm not particularly wedded to the exact name of "pool server certificate".

Still TODO: SupportedProtocolList support (prefer to do that in a separate PR).

[davidv1992]

Mostly looks good, some minor things that still need a feature flag and one style issue.

[squell]

Note; this does not actually add client TLS certificate to the live server; that requires implementing an own ClientCertVerifier.