major changes for 1.4.0 (dagster-io#15431)

## Summary & Motivation

## How I Tested These Changes

CHANGES.md

@@ -2,6 +2,27 @@
 
 # 1.4.0 / 0.20.0 (libraries) "Material Girl"
 
+## ****Major Changes since 1.3.0 (core) / 0.19.0 (libraries)****
+
+### Core
+
+- **Auto-materialize history** – We’ve added a UI that tracks why assets were or were not materialized according to their`AutoMaterializePolicy`. It’s located under `Assets` → Select an asset with an `AutoMaterializePolicy` → `Auto-materialize history` tab.
+- **********Auto-materialize performance********** – We’ve made significant performance improvements to the Asset Daemon, allowing it to keep up with asset graphs containing thousands of assets and assets with a large history of previously-materialized partitions.
+- **Asset backfill cancellation** — Asset backfills can now be canceled, bring them to parity with job backfills. When an asset backfill is requested for cancellation, the daemon cancels runs until all runs are terminated, then marks the backfill as “canceled”.
+- **non_argument_deps → deps** – We’ve deprecated the `non_argument_deps` parameter of `@asset` and `@multi_asset` in favor of a new `deps` parameter. The new parameter makes it clear that this is a first-class way of defining dependencies, makes code more concise, and accepts `AssetsDefinition` and `SourceAsset` objects, in addition to the `str`s and `AssetKey`s that the previous parameter accepted.
+- **Group-level asset status UI** – the new Assets Overview dashboard, located underneath the Activity tab of the Overview page, shows the status all the assets in your deployment, rolled up by group.
+- **Op concurrency (experimental)** — We’ve added a feature that allows limiting the number of concurrently executing ops across runs. [[docs](https://docs.dagster.io/guides/limiting-concurrency-in-data-pipelines#limiting-opasset-concurrency-across-runs)]
+- `DynamicPartitionsDefinition` and `SensorResult` are no longer marked experimental.
+- **********************************************************************Automatically observe source assets, without defining jobs (experimental)********************************************************************** – The `@observable_source_asset` decorator now accepts an `auto_observe_interval_minutes` parameter. If the asset daemon is turned on, then the observation function will automatically be run at this interval. Downstream assets with eager auto-materialize policies will automatically run if the observation function indicates that the source asset has changed. [[docs](https://docs.dagster.io/concepts/assets/asset-auto-execution#auto-materialize-policies-and-data-versions)]
+- **********Dagit → Dagster UI********** – To reduce the number of Dagster-specific terms that new users need to learn when learning Dagster, “Dagit” has been renamed to the “The Dagster UI”. The `dagit` package is deprecated in favor of the `dagster-webserver` package.
+- ****************************************************************Default config in the Launchpad**************************************************************** - When you open the launchpad to kick off a job or asset materialization, Dagster will now automatically populate the default values for each field.
+
+### dagster-dbt
+
+- The **new `@dbt_assets` decorator** allows much more control over how Dagster runs your dbt project. [[docs](https://docs.dagster.io/_apidocs/libraries/dagster-dbt#dagster_dbt.dbt_assets)]
+- The **new `dagster-dbt project scaffold` command line interface** makes it easy to create files and directories for a Dagster project that wraps an existing dbt project.
+- **Improved APIs for defining asset dependencies** – The new `get_asset_key_for_model` and `get_asset_key_for_source` utilities make it easy to specify dependencies between upstream dbt assets and downstream non-dbt assets. And you can now more easily specify dependencies between dbt models and upstream non-dbt assets by specifying Dagster asset keys in the dbt metadata for dbt sources.
+
 ## **Since 1.3.14 (core) / 0.19.14 (libraries)**
 
 ### New