utils: add safety_macros codegen script

[camshaft]

This change continues the S2N_RESULT migration. In this phase, we add a codegen script to consistently generate all safety macros.

This also changes the macros to explicitly state the context in which it should be used. For example, if a safety macro is used in a function that returns an int (i.e. POSIX), safety calls would include POSIX_GUARD, POSIX_ENSURE, etc. If the function returns S2N_RESULT, calls should be prefixed with RESULT_ (e.g. RESULT_GUARD, RESULT_ENSURE). You can see a list of all of the calls in the auto-generated documentation.

Callouts

• One thing to note is the RESULT_ prefix is temporary. After this PR is merged and other existng PRs apply the codemod script, we will have another PR that removes the RESULT_ prefix and makes S2N_RESULT the preferred error signal return type. Without an intermediate phase, the codemod script will not be idempotent, since all of the prefix-less calls will be ambiguous.

• Another point is that all of the existing safety macros are unmodified. After applying the codemod script from utils: add safety codemod script #2339, the existing safety macros will be removed in favor of the new naming convention.

Rendered documentation

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

[codecov-io]

Codecov Report

Merging #2423 (040ee91) into main (cf32218) will increase coverage by 0.03%.
The diff coverage is 98.43%.

@@            Coverage Diff             @@
##             main    #2423      +/-   ##
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+ Coverage   81.96%   81.99%   +0.03%     
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  Files         271      272       +1     
  Lines       18676    18726      +50     
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+ Hits        15307    15354      +47     
- Misses       3369     3372       +3