[SPARK-35393][PYTHON][INFRA][TESTS] Recover pip packaging test in Github Actions

Currently pip packaging test is being skipped:

```
========================================================================
Running PySpark packaging tests
========================================================================
Constructing virtual env for testing
Missing virtualenv & conda, skipping pip installability tests
Cleaning up temporary directory - /tmp/tmp.iILYWISPXW
```

See https://github.com/apache/spark/runs/2568923639?check_suite_focus=true

GitHub Actions's image has its default Conda installed at `/usr/share/miniconda` but seems like the image we're using for PySpark does not have it (which is legitimate).

This PR proposes to install Conda to use in pip packaging tests in GitHub Actions.

To recover the test coverage.

No, dev-only.

It was tested in my fork: https://github.com/HyukjinKwon/spark/runs/2575126882?check_suite_focus=true

```
========================================================================
Running PySpark packaging tests
========================================================================
Constructing virtual env for testing
Using conda virtual environments
Testing pip installation with python 3.6
Using /tmp/tmp.qPjTenqfGn for virtualenv
Collecting package metadata (current_repodata.json): ...working... done
Solving environment: ...working... failed with repodata from current_repodata.json, will retry with next repodata source.
Collecting package metadata (repodata.json): ...working... done
Solving environment: ...working... done

  environment location: /tmp/tmp.qPjTenqfGn/3.6

  added / updated specs:
    - numpy
    - pandas
    - pip
    - python=3.6
    - setuptools

...

Successfully ran pip sanity check
```

Closes #32537 from HyukjinKwon/SPARK-35393.

Authored-by: Hyukjin Kwon <gurwls223@apache.org>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
(cherry picked from commit 7d371d2)
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>

Author: HyukjinKwon

.github/workflows/build_and_test.yml

@@ -76,8 +76,6 @@ jobs:
       INCLUDED_TAGS: ${{ matrix.included-tags }}
       HADOOP_PROFILE: ${{ matrix.hadoop }}
       HIVE_PROFILE: ${{ matrix.hive }}
-      # GitHub Actions' default miniconda to use in pip packaging test.
-      CONDA_PREFIX: /usr/share/miniconda
       GITHUB_PREV_SHA: ${{ github.event.before }}
       SPARK_LOCAL_IP: localhost
     steps:
@@ -160,8 +158,6 @@ jobs:
       MODULES_TO_TEST: ${{ matrix.modules }}
       HADOOP_PROFILE: hadoop2.7
       HIVE_PROFILE: hive2.3
-      # GitHub Actions' default miniconda to use in pip packaging test.
-      CONDA_PREFIX: /usr/share/miniconda
       GITHUB_PREV_SHA: ${{ github.event.before }}
       SPARK_LOCAL_IP: localhost
     steps:
@@ -195,13 +191,18 @@ jobs:
       with:
         python-version: 2.7
         architecture: x64
-    - name: Install Python packages (Python 2.7 )
+    - name: Install Python packages (Python 2.7)
       run: |
         python2.7 -m pip install numpy 'pyarrow<3.0.0' pandas scipy xmlrunner
         python2.7 -m pip list
+    - name: Install Conda for pip packaging test
+      run: |
+        curl -s https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh > miniconda.sh
+        bash miniconda.sh -b -p $HOME/miniconda
     # Run the tests.
     - name: Run tests
       run: |
+        export PATH=$PATH:$HOME/miniconda/bin
         ./dev/run-tests --parallelism 2 --modules "$MODULES_TO_TEST"
     - name: Upload test results to report
       if: always()

dev/run-pip-tests

@@ -80,10 +80,6 @@ for python in "${PYTHON_EXECS[@]}"; do
     VIRTUALENV_PATH="$VIRTUALENV_BASE"/$python
     rm -rf "$VIRTUALENV_PATH"
     if [ -n "$USE_CONDA" ]; then
-      if [ -f "$CONDA_PREFIX/etc/profile.d/conda.sh" ]; then
-        # See also https://github.com/conda/conda/issues/7980
-        source "$CONDA_PREFIX/etc/profile.d/conda.sh"
-      fi
       conda create -y -p "$VIRTUALENV_PATH" python=$python numpy pandas pip setuptools
       source activate "$VIRTUALENV_PATH" || conda activate "$VIRTUALENV_PATH"
     else