Move RcuVector and relevant support classes to vespalib

Having RCU support available across all our C++ modules open up
new opportunities for optimizations.

This changes the following:
- `RcuVector` moved from `searchlib` to `vespalib`
- `MemoryUsage` moved from `searchlib` to `vespalib`
- Introduce a simplified, more generic `GrowStrategy` in `vespalib`
  used by the moved `RcuVector` which does not have any notion of
  documents. Existing searchlib `GrowStrategy` gets a simple function
  to convert to this generic strategy.

1 files changed, 1 insertions, 1 deletions

diff --git a/searchlib/src/tests/attribute/reference_attribute/reference_attribute_test.cpp b/searchlib/src/tests/attribute/reference_attribute/reference_attribute_test.cpp
index def939aa725..e534153d004 100644
--- a/searchlib/src/tests/attribute/reference_attribute/reference_attribute_test.cpp
+++ b/searchlib/src/tests/attribute/reference_attribute/reference_attribute_test.cpp
@@ -12,7 +12,7 @@ LOG_SETUP("reference_attribute_test");
 #include <vespa/searchlib/test/mock_gid_to_lid_mapping.h>
 #include <vespa/document/base/documentid.h>
 
-using search::MemoryUsage;
+using vespalib::MemoryUsage;
 using vespalib::ArrayRef;
 using generation_t = vespalib::GenerationHandler::generation_t;
 using search::attribute::Reference;