Expose more usbdev_stream methods

- Expose a few methods in USBDevStream that were previously protected.
- Mark the `main` method in the stream_test library as weak, so it can
  be overridden by downstream users.

Change-Id: If1254375409a837efb0f4e5e59143cb2dae41d14

sw/host/tests/usbdev/usbdev_stream/stream_test.cc

diff --git a/sw/host/tests/usbdev/usbdev_stream/stream_test.cc b/sw/host/tests/usbdev/usbdev_stream/stream_test.cc
index 0b042a6..5fcae50 100644
--- a/sw/host/tests/usbdev/usbdev_stream/stream_test.cc
+++ b/sw/host/tests/usbdev/usbdev_stream/stream_test.cc
@@ -482,6 +482,7 @@
   return 0;
 }
 
+__attribute__((weak))
 int main(int argc, char *argv[]) {
   const uint16_t kVendorID = 0x18d1u;
   const uint16_t kProductID = 0x503au;

sw/host/tests/usbdev/usbdev_stream/usbdev_stream.h

diff --git a/sw/host/tests/usbdev/usbdev_stream/usbdev_stream.h b/sw/host/tests/usbdev/usbdev_stream/usbdev_stream.h
index 9012422..d722d42 100644
--- a/sw/host/tests/usbdev/usbdev_stream/usbdev_stream.h
+++ b/sw/host/tests/usbdev/usbdev_stream/usbdev_stream.h
@@ -176,6 +176,26 @@
     }
   }
 
+  /**
+   * Add the specified number of bytes to the circular buffer; if `data` is NULL
+   * then the bytes shall already be present in the buffer and copying is not
+   * performed.
+   *
+   * @param  data    The data to be added to the buffer, or NULL
+   * @param  len     The number of bytes to be added.
+   * @return The success of the operation.
+   */
+  bool AddData(const uint8_t *data, uint32_t len);
+  /**
+   * Returns the amount of contiguous free space available in the buffer,
+   * and optionally a pointer to the start of the free space.
+   *
+   * @param  space    Receives the pointer to the start of the free space,
+   *                  or NULL iff pointer not required.
+   * @return The contiguous free space available (in bytes).
+   */
+  uint32_t SpaceAvailable(uint8_t **space);
+
  protected:
   /**
    * Provision the given number of bytes of contiguous space,
@@ -188,25 +208,6 @@
    */
   bool ProvisionSpace(uint8_t **space, uint32_t len);
   /**
-   * Returns the amount of contiguous free space available in the buffer,
-   * and optionally a pointer to the start of the free space.
-   *
-   * @param  space    Receives the pointer to the start of the free space,
-   *                  or NULL iff pointer not required.
-   * @return The contiguous free space available (in bytes).
-   */
-  uint32_t SpaceAvailable(uint8_t **space);
-  /**
-   * Add the specified number of bytes to the circular buffer; if `data` is NULL
-   * then the bytes shall already be present in the buffer and copying is not
-   * performed.
-   *
-   * @param  data    The data to be added to the buffer, or NULL
-   * @param  len     The number of bytes to be added.
-   * @return The success of the operation.
-   */
-  bool AddData(const uint8_t *data, uint32_t len);
-  /**
    * Record that the specified number of bytes have been added to the circular
    * buffer. The space must already have provisioned and the data bytes shall
    * already be in the buffer.