New dashboard: group migration, showing groups that failed to migrate. (

#2333)

## Changes

This PR introduces a new dashboard focused on group migration. It
currently has a widget that displays messages relating to groups that
failed to migrate properly as part of the `migrate-groups-experimental`
workflow.

### Linked issues

Resolves #1914.

### Functionality

 - New dashboard: `UCX Migration (Groups)`

### Tests

- manually tested
- verified on staging environment (screenshot to be attached)

src/databricks/labs/ucx/queries/migration/groups/00_0_migration_overview.md

@@ -0,0 +1,26 @@
+---
+height: 5
+---
+
+Workspace Group Migration
+=========================
+
+[Quick link to the group migration documentation.](https://github.com/databrickslabs/ucx/blob/main/docs/local-group-migration.md)
+
+Prerequisites for group migration are:
+
+ - The assessment workflow has completed.
+ - For each workspace group a corresponding account-level group must exist.
+
+Group migration performs the following steps:
+
+1. Workspace groups are renamed to a temporary name.
+2. The account-level groups are then provisioned into the workspace.
+3. Permissions assigned to the workspace groups are replicated on the account-level groups.
+
+These steps are performed by either the `migrate-groups` or the `migrate-groups-experimental` workflows. (The latter uses a faster, but experimental, method to replicate group permissions.)
+
+Once group migration has taken place:
+
+ - The `validate-groups-permissions` workflow can be used to check that permissions were correctly duplicated.
+ - The `remove-workspace-local-backup-groups` workflow can be used to remove the (original) workspace-level groups.

src/databricks/labs/ucx/queries/migration/groups/01_0_group_migration_failures.md

@@ -0,0 +1,11 @@
+---
+height: 4
+width: 2
+---
+
+Group Migration Failures
+------------------------
+
+When migrating groups, errors may occur during the migration of a particular group. Any errors that occurred while migrating groups are displayed here.
+
+The errors for all workflow runs are shown; to clear (old) errors the job run can be deleted.

src/databricks/labs/ucx/queries/migration/groups/01_1_group_migration_failures.sql

@@ -0,0 +1,15 @@
+/* --title 'Group Migration Failures' --height 4 --width 4 */ /*
+ *
+ * Messages that we're looking for are of the form:
+ *   failed-group-migration: {name_in_workspace} -> {name_in_account}: {reason}
+ */
+SELECT
+  FROM_UNIXTIME(timestamp) AS timestamp,
+  job_run_id,
+  level,
+  message
+FROM inventory.logs
+WHERE
+  workflow_name IN ('migrate-groups', 'migrate-groups-experimental') AND STARTSWITH(message, 'failed-group-migration:')
+ORDER BY
+  1