Refactor of config pkg

[capri-xiyue]

TL;DR

There are some duplicates when loading config from env, do validation and set defaults.
https://github.com/abcxyz/jvs/blob/main/pkg/config/public_key_config.go#L43 and

jvs/pkg/config/crypto_config.go

Line 102 in 23cdda1

func loadCryptoConfigFromLookuper(ctx context.Context, b []byte, lookuper envconfig.Lookuper) (*CryptoConfig, error) {

.

We can do refactor to avoid duplicates.

Detailed design

Create a common function which handles loading config from env with any parameter. The caller of the common function need to pass the pointer of specific config like PublicKeyConfig or CryptoConfig as the value of any parameter.

Alternatives considered

No response

Additional information

No response

[yolocs]

Added a lib in pkg: abcxyz/pkg#33

[yolocs]

Adopt pkg/cfgloader wherever applicable