refactor role package

[kyfujisa]

The access token feature added in this PR #56 is implemented in the role package.
It should be divided into access packages.

[kyfujisa]

I think it would be good to match this to atpParams.

athenz-authorizer/role/processor.go

Lines 45 to 49 in 930b45d

	enableMTLSCertificateBoundAccessToken bool
	// If you go back to the issue time, set that time. Subtract if necessary (for example, token issuance time).
	clientCertificateGoBackSeconds int64
	// The number of seconds to allow for a failed CNF check due to a client certificate being updated.
	clientCertificateOffsetSeconds int64

athenz-authorizer/option.go

Lines 44 to 47 in 930b45d

	type ATProcessorParam struct {
	verifyCertThumbprint bool
	certBackdateDur string
	certOffsetDur string

[WindzCUHK]

TODO: add test cases for *Verifier := wrapper functions in func (a *authorizer) initVerifiers() error

[WindzCUHK]

continue in: AthenZ/athenz-authorizer#5