Switch the license to Apache 2.0, matching OpenSSL upstream · google/boringssl@33d1049 · GitHub

We use the standard Apache 2.0 file header, described in "APPENDIX: How
to apply the Apache License to your work."

This was primarily automated by running:

  git ls-tree -r --name-only HEAD | xargs go run ./util/relicense.go

See go/boringssl-relicensing-triage for the results of triaging the
output of the tool.

As part of this, switch from taking fiat-crypto under MIT license to
Apache 2.0. (It is licensed under MIT OR Apache-2.0 OR BSD-1-Clause.)

The copyright_summary tool can also be used to confirm we didn't
accidentally drop any copyright lines:

  # Run before the CL
  git grep -l Copyright | xargs go run ./util/copyright_summary.go  -out /tmp/old.json
  # Run after the CL
  git grep -l Copyright | xargs go run ./util/copyright_summary.go  -compare /tmp/old.json

Bug: 364634028
Change-Id: I17c50e761e9d077a1f92e25969e50ed35e320c59
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/75852
Reviewed-by: Bob Beck <bbe@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>