Check provider database with CI

scripts/update-provider-database.sh checks out the provider database
and updates data.rs file,
making it easier to update.

CI uses this script to check that checked in data.rs
corresponds to the provider database repository.

scripts/update-provider-database.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+# Updates provider database.
+# Returns 1 if the database is changed, 0 otherwise.
+set -euo pipefail
+
+export TZ=UTC
+
+# Provider database revision.
+REV=3c8f7e846c915a183dc44536fb5480d1f25d7c42
+
+CORE_ROOT="$PWD"
+TMP="$(mktemp -d)"
+git clone --filter=blob:none https://github.com/deltachat/provider-db.git "$TMP"
+cd "$TMP"
+git checkout "$REV"
+DATE=$(git show -s --format=%cs)
+"$CORE_ROOT"/scripts/update-provider-database.py "$TMP/_providers" "$DATE" >"$CORE_ROOT/src/provider/data.rs"
+rustfmt "$CORE_ROOT/src/provider/data.rs"
+rm -fr "$TMP"
+
+cd "$CORE_ROOT"
+test -z "$(git status --porcelain src/provider/data.rs)"