cli-altsrc and cli-docs version drift and incompatibilities

[bartekpacia]

What's the problem?

The latest urfave/cli (v3.0.0-alpha9.2), is not compatible with the latest urfave/cli-docs (v3.0.0-alpha5).

Attempting to build a project with those 2 dependencies results in:

~/projects/emu git:[master]
go build ./cmd/emu/
# github.com/urfave/cli-docs/v3
../../.cache/go/pkg/mod/github.com/urfave/cli-docs/v3@v3.0.0-alpha5/docs.go:273:16: flag.GetValue undefined (type cli.DocGenerationFlag has no field or method GetValue)
../../.cache/go/pkg/mod/github.com/urfave/cli-docs/v3@v3.0.0-alpha5/docs.go:400:21: flag.GetValue undefined (type cli.DocGenerationFlag has no field or method GetValue)

for a sample reproducer, see bartekpacia/emu#7

What's the larger problem?

There's no CI checks that prevent this kind of problem.

Ideally, nothing that breaks compatibility between the urfave/cli modules (cli, altsrc, and docs) should be mergeable (i.e. CI should be red), unless explicit approval from maintainers.