fix: configurable temp file directory #1030

Job	Run time
examples / multirepo (ubuntu-latest)	5s
examples / client (ubuntu-latest)	7s
examples / multirepo (macos-latest)	16s
examples / client (macos-latest)	13s
examples / multirepo (windows-latest)	1m 23s
examples / client (windows-latest)	2m 48s
examples / repository (ubuntu-latest)	7s
examples / repository (macos-latest)	14s
examples / repository (windows-latest)	1m 5s
examples / root-signing (ubuntu-latest)	19s
examples / tuf-client-cli (ubuntu-latest)	14s
examples / root-signing (macos-latest)	20s
examples / tuf-client-cli (macos-latest)	19s
linting / golangci-lint	22s
examples / root-signing (windows-latest)	1m 54s
examples / tuf-client-cli (windows-latest)	1m 49s
linting / govulncheck	16s
tests / Run (ubuntu-latest)	31s
tests / Run (macos-latest)	40s
tests / Run (windows-latest)	2m 21s
	15m 23s

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