TextLoader method override detection

[tmat]

Implements pattern used by BCL to deprecate public abstract methods:

• Update old method to call the new method.
• Change abstract to virtual if needed
• New method:
  • Use reflection to ask if the old method was overridden.
  • If it was overridden, call it, otherwise call old method.

We can still stack overflow if the old method is overridden but calls the base implementation.

[tmat]

@333fred @jasonmalinowski @AlekseyTs

[AlekseyTs]

Done with review pass (commit 1)

[AlekseyTs]

Done with review pass (commit 1 vs. 2)

[AlekseyTs]

Done with review pass (commit 5)

[tmat]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 4 pipeline(s).