[vpr] doc update

Author: oscarcheng105

libs/librrgraph/src/base/SCHEMA_GENERATOR.md

@@ -6,30 +6,30 @@ mediated via RrGraphBase located in `rr_graph_uxsdcxx_interface.h`.
 
 If `rr_graph.xsd` is modified, then the following files must be updated:
 
- - `libs/librrgraph/src/base/gen/rr_graph_uxsdcxx.h`
- - `libs/librrgraph/src/base/gen/rr_graph_uxsdcxx_capnp.h`
- - `libs/librrgraph/src/base/gen/rr_graph_uxsdcxx_interface.h`
+ - `libs/librrgraph/src/io/gen/rr_graph_uxsdcxx.h`
+ - `libs/librrgraph/src/io/gen/rr_graph_uxsdcxx_capnp.h`
+ - `libs/librrgraph/src/io/gen/rr_graph_uxsdcxx_interface.h`
  - `libs/libvtrcapnproto/rr_graph_uxsdcxx.capnp`
 
 ### Instructions to update generated files (using CMake)
 
 1. Run target `generate_rr_graph_serializers`, e.g. run `make generate_rr_graph_serializers`.
 2. Run target `format`, e.g. run `make format`.
-3. Update `libs/librrgraph/src/base/rr_graph_uxsdcxx_interface_impl.h`, implement or
+3. Update `libs/librrgraph/src/io/rr_graph_uxsdcxx_interface_impl.h`, implement or
    update interfaces that are new or are changed.  The compiler will complain
    that virtual methods are missing if the schema has changed.
 
 ### Instructions to update generated files (manually)
 
 1. Clone https://github.com/duck2/uxsdcxx/
 2. Run `python3 -mpip install --user -r requirements.txt`
-3. Run `python3 uxsdcxx.py libs/librrgraph/src/base/rr_graph.xsd`
-3. Run `python3 uxsdcap.py libs/librrgraph/src/base/rr_graph.xsd`
+3. Run `python3 uxsdcxx.py libs/librrgraph/src/io/rr_graph.xsd`
+3. Run `python3 uxsdcap.py libs/librrgraph/src/io/rr_graph.xsd`
 4. Copy `rr_graph_uxsdcxx.h`, `rr_graph_uxsdcxx_capnp.h`,
-   `rr_graph_uxsdcxx_interface.h` to `libs/librrgraph/src/base/`
+   `rr_graph_uxsdcxx_interface.h` to `libs/librrgraph/src/io/`
 5. Copy `rr_graph_uxsdcxx.capnp` to `../libvtrcapnproto/`
 6. Run `make format`
-7. Update `libs/librrgraph/src/base/rr_graph_uxsdcxx_interface_impl.h`, implement or
+7. Update `libs/librrgraph/src/io/rr_graph_uxsdcxx_interface_impl.h`, implement or
    update interfaces that are new or are changed.  The compiler will complain
    that virtual methods are missing if the schema has changed.