Use eh2_* namespace from renamed erlang_h2 (companion to erlang_h2#19, refs #893)

[walki]

Use the eh2_* namespace from renamed erlang_h2

Companion to benoitc/erlang_h2#19; part of fixing #893.

Why

hackney 4.x bundles erlang_h2, whose h2_* module names collide with chatterbox (pulled via grpcbox ← opentelemetry_exporter). Because BEAM module names are global atoms, any app depending on both hackney 4.x and opentelemetry_exporter can't assemble a release:

** (Mix) Duplicated modules:
    h2_settings / h2_frame / h2_connection / h2_client specified in chatterbox and h2

erlang_h2#19 renames those modules to the eh2_* namespace. This is the matching hackney-side update.

Change

hackney references erlang_h2 only through the connection module, so this is small:

• h2_connection → eh2_connection (27 call sites in hackney_conn.erl and hackney_h2_stream.erl).

The public h2 API module, the {h2, Conn, ...} message tag, the OTP app name h2, and the dialyzer plt_extra_apps entry are all unchanged.

Dependency note

This branch temporarily points the h2 dep at the rename branch so it builds and can be verified end-to-end:

{h2, {git, "https://github.com/walki/erlang_h2.git", {branch, "fix-h2-module-namespace-collision"}}}

Once erlang_h2#19 is merged and released, this should go back to the hex version ({h2, "~> <renamed release>"}). Happy to update once you cut that release.

Verification

Built end-to-end against a real downstream app (Phoenix + opentelemetry_exporter + ex_aws on hackney): rebar3 compile clean, and the consuming app's mix release now assembles with no duplicated-modules error.

webtransport also references the renamed modules (h2_varint, h2_capsule) and would need the same one-line-namespace update; flagged in erlang_h2#19. Glad to send that PR too.