Cleanup EVP_PKEY serialization #1314

Job	Run time
apidiff (aws-lc-sys, branch)	2m 47s
apidiff (aws-lc-sys, published)	3m 7s
apidiff (aws-lc-fips-sys, branch)	4m 48s
apidiff (aws-lc-fips-sys, published)	3m 50s
apidiff (aws-lc-rs, branch)	2m 45s
apidiff (aws-lc-rs, published)	2m 59s
bindgen-dependency (ubuntu-latest)	22s
bindgen-dependency (macos-13)	39s
bindgen-dependency (macos-14-xlarge)	25s
bindgen-dependency (windows-latest)	58s
bindgen-fips-dependency (ubuntu-latest)	22s
bindgen-fips-dependency (macos-13)	34s
bindgen-fips-dependency (macos-14-xlarge)	23s
bindgen-fips-dependency (windows-latest)	1m 1s
clippy (aws-lc-rs, --features bindgen,unstable)	1m 15s
dependency-review	22s
clippy (aws-lc-rs, --features bindgen,unstable,fips)	1m 43s
metadata-checks	30s
Resolve the dependencies to the minimum SemVer version (aws-lc-rs)	54s
clippy (aws-lc-rs, --no-default-features --features aws-lc-sys)	49s
Resolve the dependencies to the minimum SemVer version (aws-lc-sys)	41s
rustfmt	25s
semver-checks	1m 32s
Resolve the dependencies to the minimum SemVer version (aws-lc-fips-sys)	1m 15s
udeps	8m 14s
	42m 40s

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