Backport of Trap errors related to vault pki list-intermediate issuer reading into release/1.13.x

[hc-github-team-secure-vault-core]

Backport

This PR is auto-generated from #19165 to be assessed for backporting due to the inclusion of the label backport/1.13.x.

WARNING automatic cherry-pick of commits failed. Commits will require human attention.

merge conflict error: POST https://api.github.com/repos/hashicorp/vault/merges: 409 Merge conflict []

The below text is copied from the body of the original PR.

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Description

Discovered during testing if an invalid parent issuer url was provided to the list-intermediate pki sub-command we would get a nil exception.

What was modified

• Factor out reading issuers into a common method that will parse and validate the response (certificate, key_id, ca chain)
• Leverage some of the existing methods from the pki healthcheck to parse the issuer response
• Change the list-intermediate command to load the parent issuer only once, instead of every child issuer.

Encountered error being addressed

❯ vault pki list-intermediates pki
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x53035a4]

goroutine 1 [running]:
github.com/hashicorp/vault/command.verifySignBetween(0xc00151a280, {0x7ff7bfeff99d, 0x3}, {0xc0006e8660, 0x2f})
        /Users/sclark/git-repos/vault-oss/command/pki_verify_sign_command.go:115 +0x144
github.com/hashicorp/vault/command.(*PKIListIntermediateCommand).Run(0xc0012ee180, {0xc0000720b0, 0x1, 0x1})
        /Users/sclark/git-repos/vault-oss/command/pki_list_intermediate_command.go:192 +0x7e5
github.com/mitchellh/cli.(*CLI).Run(0xc000304000)
        /Users/sclark/go/pkg/mod/github.com/mitchellh/cli@v1.1.2/cli.go:262 +0x5f8
github.com/hashicorp/vault/command.RunCustom({0xc000072090?, 0x3?, 0x3?}, 0xc0000061a0?)
        /Users/sclark/git-repos/vault-oss/command/main.go:238 +0xa65
github.com/hashicorp/vault/command.Run(...)
        /Users/sclark/git-repos/vault-oss/command/main.go:142
main.main()
        /Users/sclark/git-repos/vault-oss/main.go:16 +0x50

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Overview of commits

• 7d9dd37

[hashicorp-cla]

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