Add math udf

[yuancu]

Description

Implement math UDFs, their unit tests, and their integration tests.

Integration Test Coverage

Functions	Covered by Spark IT	Covered by IT
abs	Y	Y
acos		Y
asin		Y
atan		Y
atan2		Y
cbrt		Y
ceiling	Y	Y
conv		Y
cos		Y
cot		Y
crc32		Y
degrees		Y
e		Y
exp		Y
floor	Y	Y (Modified)
ln	Y	Y
log		Y
log2		Y
log10		Y
mod	Y	Y
pi		Y
pow	Y	Y
radians		Y
rand		Y
round		Y
sign		Y
sin		Y
sqrt	Y	Y

The integration tests covered by Spark are copied to this IT (Apart from floor). The rest is implemented by ourselves.

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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