Adding wrappers for CSR Generation

[dgarske]

• Support for wolfTPM2_CSR_Generate wrapper to assist with CSR generation.
• Modified the existing CSR example to use wrapper.
• Adds support for WOLFTPM2_CSR structure and using custom OIDs in the CSR. This allows passing a WOLFTPM2_CSR to a set of new wolfTPM2_CSR_* API's.
• Added CSharp wrappers and tests for CSR feature.

The custom OID feature requires:

user_settings.h:

#define WOLFSSL_ASN_TEMPLATE
#define WOLFSSL_CUSTOM_OID
#define HAVE_OID_ENCODING

Cmake:

"CMAKE_C_FLAGS": "-DWOLFSSL_CUSTOM_OID -DHAVE_OID_ENCODING -DWOLFSSL_ASN_TEMPLATE",

Configure (autoconf):

./configure --enable-wolftpm --enable-certgen --enable-asn=template CFLAGS="-DWOLFSSL_CUSTOM_OID -DHAVE_OID_ENCODING"

[dgarske]

Note: Going to be adding a WOLFTPM_CSR struct / class to support assembling a CSR then asking for it to be signed. This will allow for the custom request extension support.