fix: "default" proposal and extension types MUST NOT be listed in capabilities

[mulmarta]

The PR makes the implementation conformant with the following rule mandated by RFC 9420, Section 7.2:

The capabilities field indicates the protocol features that the client supports, including protocol versions, cipher suites, credential types, non-default proposal types, and non-default extension types. The following proposal and extension types are considered "default" and MUST NOT be listed
[...]

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

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.52%. Comparing base (0e602b4) to head (40040c5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #319      +/-   ##
==========================================
+ Coverage   88.50%   88.52%   +0.01%     
==========================================
  Files         182      182              
  Lines       29002    29043      +41     
==========================================
+ Hits        25668    25709      +41     
  Misses       3334     3334              

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