Add backward compatibility workflow and tests.

Suppose we have umfFunc_0_11 and umfFunc_0_10. With this PR:

• "umfFunc" == "umfFunc_0_11" in compile time (using #define)
• UMF exports 2 symbols: "umfFunc@@UMF_0.10" and "umfFunc_0_11@@UMF_0.11"
• dlsym("umfFunc") == "umfFunc_0_10"
• dlsym("umfFunc_0_11") == "umfFunc_0_11"

Major changes:

• use UMF_PROVIDER_OPS_VERSION_CURRENT and UMF_POOL_OPS_VERSION_CURRENT for versioning memory provider and pools struct instead of UMF_VERSION_CURRENT that would be used only for versioning the lib
• add new implementation for umfDevDaxMemoryProviderOps and umfFileMemoryProviderOps ver 0.11
• handle old (0.10) provider ops in umfMemoryProviderCreate
• do not assert when the user pass an old provider/pool version of ops to umfMemoryProvider/PoolCreate and print a warning instead
• add tests for multiple symbols (file and DevDax providers ops) - assume that calling dlsym without a specified version returns the oldest implementation

fixes #908