packer: update to 1.8.7

Pkgsrc changes:

* Update MAINTAINER mail address.
* Specify correct version number using ldflags.

Upstream changes:

PLUGINS

* core: Migrate external Linode plugin to linode/packer-plugin-linode.
* core: Migrate external UCloud plugin to ucloud/packer-plugin-ucloud.
* core: Remove external plugin for Digital Ocean as a vendored plugin.
* core: Remove external plugins for Profitbricks and 1&1 as vendored
  plugins.
* docs: Add HCP Ready label to Oracle builder components.

IMPROVEMENTS

* cmd/console: Add config-type flag to command help.
* core: Add enhanced support to Packer telemetry for HCL2.
* Enhance zsh completion for the Packer command.

BUG FIXES

* cmd/hcl2_upgrade: Fix a crash when running the hcl2_upgrade command
  against a legacy JSON template containing user variables with an undefined
  variables block.
* core: Bump github.com/hashicorp/hcp-sdk-go to 0.36.0.
* core: Bump github.com/hashicorp/packer-plugin-sdk to 0.4.0 to address
  CVE-2023-0475, CVE-2022-41723.
* core: Bump Go module version to 1.20
* core: Fix regression introduced in 1.8.6, where legacy JSON templates
  with custom builder names are outputted to STDOUT as uninterpolated user
  variables.

(iquiw)