### What changes were proposed in this pull request?
This PR proposes to deprecate the APIs at `SQLContext` removed in SPARK-25908. We should remove equivalent APIs; however, seems we missed to deprecate.
While I am here, I fix one more issue. After SPARK-25908, `sc._jvm.SQLContext.getOrCreate` dose not exist anymore. So,
```python
from pyspark.sql import SQLContext
from pyspark import SparkContext
sc = SparkContext.getOrCreate()
SQLContext.getOrCreate(sc).range(10).show()
```
throws an exception as below:
```
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/.../spark/python/pyspark/sql/context.py", line 110, in getOrCreate
jsqlContext = sc._jvm.SQLContext.getOrCreate(sc._jsc.sc())
File "/.../spark/python/lib/py4j-0.10.8.1-src.zip/py4j/java_gateway.py", line 1516, in __getattr__
py4j.protocol.Py4JError: org.apache.spark.sql.SQLContext.getOrCreate does not exist in the JVM
```
After this PR:
```
/.../spark/python/pyspark/sql/context.py:113: DeprecationWarning: Deprecated in 3.0.0. Use SparkSession.builder.getOrCreate() instead.
DeprecationWarning)
+---+
| id|
+---+
| 0|
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+---+
```
In case of the constructor of `SQLContext`, after this PR:
```python
from pyspark.sql import SQLContext
sc = SparkContext.getOrCreate()
SQLContext(sc)
```
```
/.../spark/python/pyspark/sql/context.py:77: DeprecationWarning: Deprecated in 3.0.0. Use SparkSession.builder.getOrCreate() instead.
DeprecationWarning)
```
### Why are the changes needed?
To promote to use SparkSession, and keep the API party consistent with Scala side.
### Does this PR introduce any user-facing change?
Yes, it will show deprecation warning to users.
### How was this patch tested?
Manually tested as described above. Unittests were also added.
Closes#27614 from HyukjinKwon/SPARK-30861.
Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
e065e22e5e