refactor ptls to clarify the difference between FIPS and non-FIPS modes

and backfill some basic tests

internal/crypto/ptls/profiles_fips_strict_test.go

@@ -0,0 +1,9 @@
+// Copyright 2024 the Pinniped contributors. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package ptls
+
+// If you are coming here to look for unit tests for the FIPS-mode profiles,
+// please instead see test/integration/ptls_fips_test.go.
+// CI does not currently run the unit tests in FIPS mode, so these unit tests
+// were instead written as integration tests.