…#15341)

#### Description

At the moment `go get go.opentelemetry.io/collector/cmd/mdatagen@main`
result in an unbuildable `mdatagen`.

This happens because mdatagen's go.mod on main references
`go.opentelemetry.io/collector/internal/schemagen v0.152.1`. `mdatagen`
was
[updated](https://github.com/open-telemetry/opentelemetry-collector/pull/15304/changes#diff-42498599bf5b805dde7cc8403116834d346c7cbb62150935aeda205a61886661R60)
to depend on a new field from `internal/schemagen` (`InternalOnly`) on
main and this new field is not in
`go.opentelemetry.io/collector/internal/schemagen v0.152.1`. When
building externally (without the replace statements) the dependency is
resolved to `v0.152.1` and the compile fails because `v0.152.1` does not
have the new field.

My fix is to bump `mdatagen`'s dependency to a psuedo version of the tip
of main. All of this will get cleaned up with the `v0.153.0` release,
but I'd like to do this now so I can bump Contrib's core deps to the tip
of main so I can handle the breaking change from
open-telemetry#15310
before the release.

#### Testing

I ran a quick test locally using this commit's psuedo version and
confirmed I was able to install mdatagen now

open-telemetry/opentelemetry-collector#15310 added two enforcements
to mdatagen: feature-gate IDs must be prefixed with `<class>.<type>.`
and reference URLs must point at GitHub issues. Many existing gates
predate these rules. Set `skip_strict_validation: true` on each
grandfathered gate so `make generate` succeeds. New gates should leave
the field unset.

Signed-off-by: Tyler Helmuth <[email protected]>