feat(pageserver): generate basebackup from aux file v2 storage (#7517)

This pull request adds the new basebackup read path + aux file write
path. In the regression test, all logical replication tests are run with
matrix aux_file_v2=false/true.

Also fixed the vectored get code path to correctly return missing key
error when being called from the unified sequential get code path.
---------

Signed-off-by: Alex Chi Z <chi@neon.tech>

test_runner/fixtures/utils.py

@@ -1,4 +1,5 @@
 import contextlib
+import enum
 import json
 import os
 import re
@@ -484,3 +485,16 @@ def assert_no_errors(log_file, service, allowed_errors):
         log.info(f"not allowed {service} error: {error.strip()}")
 
     assert not errors, f"Log errors on {service}: {errors[0]}"
+
+
+@enum.unique
+class AuxFileStore(str, enum.Enum):
+    V1 = "V1"
+    V2 = "V2"
+    CrossValidation = "CrossValidation"
+
+    def __repr__(self) -> str:
+        return f"'aux-{self.value}'"
+
+    def __str__(self) -> str:
+        return f"'aux-{self.value}'"