feat: Add Oracle table provider with rust-oracle driver

[banickn]

Implement Oracle support using rust-oracle (ODPI-C) and bb8 connection pooling. Includes comprehensive type mappings (NUMBER, DATE, TIMESTAMP, CLOB, BLOB, RAW), schema inference, and 12 integration tests.
Tested against Oracle Database 23c Free.

Note: This is my first contribution to the project. Feedback welcome! :)

[lukekim]

@banickn thank you! We actually already have a Oracle table provider in Spice (https://github.com/spiceai/spiceai/tree/trunk/crates/data_components/src/oracle). You may want to compare the implementations, and we'd be happy to contribute this too.

[banickn]

I wasn't aware of the spice.ai oracle table provider. Just for clarification, your suggestion is that I should implement the improvements from spice.ai to this PR?
Just from first glance, porting the execution plan and some type mapping would probably make sense

[banickn]

@lukekim Thanks for pointing out the implementation. That made it a lot easier. Here's a summary of the changes from my first commit.

Optimized type mappings, custom dialect for the SQL generation, chunked execution and automated session timezone handling.
Also more tests for type mappings and to verify source pushdown.
Afterwards I noticed that you used a different default ORACLE_SERVICE_NAME, maybe it makes sense to change this?