Run 'make generate' on all go.mod updates

[erikgb]

The Renovate gomodTidy post update option is not enough for dealing with multi-module Go projects. Example failing PR: cert-manager/csi-lib#114.

I wish multi-module projects were better supported in Go, and not "bolted on", as it appears to be now.

Ref. the comment I added, I would prefer to avoid tying this even more to makefile-modules, as it will make the preset unusable in projects not using makefile-modules. https://github.com/cert-manager/sample-external-issuer is such an example. I think the workaround will be to just not use this preset when makefile-modules is not enabled on the project.

Also, the currently required make go-vendor makes the Renovate run really heavy/slow. But I don't know if it can be avoided?

[Copilot]

Pull Request Overview

This PR modifies Renovate configuration to handle multi-module Go projects by replacing the gomodTidy post update option with a more comprehensive approach that runs make generate on all go.mod updates.

• Removes the gomodTidy post update option for Go modules
• Adds **/go.mod files to the post upgrade tasks that run make generate
• Includes a comment acknowledging the dependency on makefile-modules

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[Copilot]

The comment states this will break projects not using makefile-modules, but the change is being implemented anyway. Consider either: 1) Creating a separate preset for makefile-modules projects, 2) Adding conditional logic to check for makefile presence, or 3) Updating the comment to explain the rationale for this breaking change and migration path for affected projects.

Suggested change

	'**/go.mod', // This will break all projects using this preset, but not makefile-module.
	'**/go.mod',
	'**/Makefile', // Only run postUpgradeTasks if both go.mod and Makefile are present (proxy for makefile-modules usage).

[erikgb]

/cc @ThatsMrTalbot @hjoshi123 @inteon

[ThatsMrTalbot]

/lgtm
/approve

[cert-manager-prow]

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