tai64

x509-cert: rename helpers to `get_extension`/`filter_extensions` (#1497) #2114

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	1m 39s
build (1.65.0, wasm32-unknown-unknown)	1m 46s
test (1.65.0)	1m 40s
build (stable, thumbv7em-none-eabi)	23s
test (stable)	20s
build (stable, wasm32-unknown-unknown)	17s
minimal-versions / minimal-versions	25s
	6m 30s

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