This commit introduces a new MathToEmitC conversion pass that lowers
selected math operations from the Math dialect to the emitc.call_opaque
operation in the EmitC dialect.

**Supported Math Operations:**
The following operations are converted:

- math.floor -> emitc.call_opaque<"floor">
- math.round -> emitc.call_opaque<"round">
- math.exp -> emitc.call_opaque<"exp">
- math.cos -> emitc.call_opaque<"cos">
- math.sin -> emitc.call_opaque<"sin">
- math.acos -> emitc.call_opaque<"acos">
- math.asin -> emitc.call_opaque<"asin">
- math.atan2 -> emitc.call_opaque<"atan2">
- math.ceil -> emitc.call_opaque<"ceil">
- math.absf -> emitc.call_opaque<"fabs">
- math.powf -> emitc.call_opaque<"pow">

**Target Language Standards:**
The pass supports targeting different language standards:

- C99: Generates calls with suffixes (e.g., floorf, fabsf) for
single-precision floats.
- CPP11: Prepends std:: to functions (e.g., std::floor, std::fabs).

**Design Decisions:**
The pass uses emitc.call_opaque instead of emitc.call to better emulate
C-style function overloading.
emitc.call_opaque does not require a unique type signature, making it
more suitable for operations like <math.h> functions that may be
overloaded for different types.
This design choice ensures compatibility with C/C++ conventions.