Use stack of dependency resolvers (#1560)

## Changes
Implement resolvers as a stack
Implements an initial version of SysPathProvider
Eliminates horrible hacks introduced in previous PRs 

### Linked issues
#1202
Resolves #1499
Resolves #1421


### Functionality 

- [ ] added relevant user documentation
- [ ] added new CLI command
- [ ] modified existing command: `databricks labs ucx ...`
- [ ] added a new workflow
- [ ] modified existing workflow: `...`
- [ ] added a new table
- [ ] modified existing table: `...`

### Tests

- [ ] manually tested
- [x] added unit tests
- [ ] added integration tests
- [ ] verified on staging environment (screenshot attached)

@nfx this PR does not address the tactical `problem_collector`
parameter, I have created a specific issue for that
#1559

---------

Co-authored-by: Serge Smertin <serge.smertin@databricks.com>

CONTRIBUTING.md

@@ -55,6 +55,10 @@ unit test coverage suite and the clear difference between _unit tests_ and _inte
 
 See https://mypy.readthedocs.io/en/stable/cheat_sheet_py3.html for more details
 
+### `if typing.TYPE_CHECKING:` usage
+
+We don't use `if typing.TYPE_CHECKING:` in our codebase, because PyCharm and `mypy` can handle it without it and `Refactoring -> Move` may produce incorrect results.
+
 ### ..., expression has type "None", variable has type "str"
 
 * Add `assert ... is not None` if it's a body of a method. Example:

src/databricks/labs/ucx/contexts/application.py

@@ -31,6 +31,11 @@
 from databricks.labs.ucx.hive_metastore.udfs import UdfsCrawler
 from databricks.labs.ucx.hive_metastore.verification import VerifyHasMetastore
 from databricks.labs.ucx.installer.workflows import DeployedWorkflows
+from databricks.labs.ucx.source_code.notebooks.loaders import NotebookResolver, NotebookLoader, WorkspaceNotebookLoader
+from databricks.labs.ucx.source_code.files import FileLoader, LocalFileResolver, SysPathProvider
+from databricks.labs.ucx.source_code.graph import DependencyResolver, DependencyGraphBuilder
+from databricks.labs.ucx.source_code.whitelist import WhitelistResolver, Whitelist
+from databricks.labs.ucx.source_code.site_packages import SitePackagesResolver, SitePackages
 from databricks.labs.ucx.source_code.languages import Languages
 from databricks.labs.ucx.workspace_access import generic, redash
 from databricks.labs.ucx.workspace_access.groups import GroupManager
@@ -334,3 +339,56 @@ def workspace_info(self):
     @cached_property
     def verify_has_metastore(self):
         return VerifyHasMetastore(self.workspace_client)
+
+    @cached_property
+    def notebook_loader(self) -> NotebookLoader:
+        return WorkspaceNotebookLoader(self.workspace_client)
+
+    @cached_property
+    def notebook_resolver(self):
+        return NotebookResolver(self.notebook_loader)
+
+    @cached_property
+    def site_packages(self):
+        # TODO: actually load the site packages
+        return SitePackages([])
+
+    @cached_property
+    def syspath_provider(self):
+        return SysPathProvider.from_sys_path()
+
+    @cached_property
+    def file_loader(self):
+        return FileLoader(self.syspath_provider)
+
+    @cached_property
+    def site_packages_resolver(self):
+        return SitePackagesResolver(self.site_packages, self.file_loader, self.syspath_provider)
+
+    @cached_property
+    def whitelist(self):
+        # TODO: fill in the whitelist
+        return Whitelist()
+
+    @cached_property
+    def whitelist_resolver(self):
+        return WhitelistResolver(self.whitelist)
+
+    @cached_property
+    def file_resolver(self):
+        return LocalFileResolver(self.file_loader)
+
+    @cached_property
+    def dependency_resolver(self):
+        return DependencyResolver(
+            [
+                self.notebook_resolver,
+                self.site_packages_resolver,
+                self.whitelist_resolver,
+                self.file_resolver,
+            ]
+        )
+
+    @cached_property
+    def dependency_graph_builder(self):
+        return DependencyGraphBuilder(self.dependency_resolver)

src/databricks/labs/ucx/contexts/cli_command.py

@@ -18,6 +18,7 @@
 from databricks.labs.ucx.azure.locations import ExternalLocationsMigration
 from databricks.labs.ucx.azure.resources import AzureAPIClient, AzureResources
 from databricks.labs.ucx.contexts.application import GlobalContext
+from databricks.labs.ucx.source_code.notebooks.loaders import NotebookLoader, LocalNotebookLoader
 from databricks.labs.ucx.source_code.files import LocalFileMigrator
 from databricks.labs.ucx.workspace_access.clusters import ClusterAccess
 
@@ -168,6 +169,10 @@ def iam_role_migration(self):
             self.iam_credential_manager,
         )
 
+    @cached_property
+    def notebook_loader(self) -> NotebookLoader:
+        return LocalNotebookLoader(self.syspath_provider)
+
 
 class AccountContext(CliContext):
     def __init__(self, ac: AccountClient, named_parameters: dict[str, str] | None = None):

src/databricks/labs/ucx/source_code/base.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from abc import abstractmethod
 from collections.abc import Iterable
 from dataclasses import dataclass