[SPARK-28309][R][INFRA] Fix AppVeyor to run SparkR tests by avoiding to use devtools for testthat

## What changes were proposed in this pull request?

Looks `devtools` 2.1.0 is released and then our AppVeyor users the latest one.
The problem is, they added `testthat` 2.1.1+ as its dependency - https://github.com/r-lib/devtools/blob/master/DESCRIPTION#L35

Usually it should remove and reinstall it properly when we install other packages; however, seems it's being failed in AppVeyor due to the previous installation for an unknown reason.

```
[00:01:41] > devtools::install_version('testthat', version = '1.0.2', repos='https://cloud.r-project.org/')
[00:01:44] Downloading package from url: https://cloud.r-project.org//src/contrib/Archive/testthat/testthat_1.0.2.tar.gz
...
[00:02:25] WARNING: moving package to final location failed, copying instead
[00:02:25] Warning in file.copy(instdir, dirname(final_instdir), recursive = TRUE,  :
[00:02:25]   problem copying c:\RLibrary\00LOCK-testthat\00new\testthat\libs\i386\testthat.dll to c:\RLibrary\testthat\libs\i386\testthat.dll: Permission denied
[00:02:25] ** testing if installed package can be loaded from final location
[00:02:25] *** arch - i386
[00:02:26] Error: package or namespace load failed for 'testthat' in FUN(X[[i]], ...):
[00:02:26]  no such symbol find_label_ in package c:/RLibrary/testthat/libs/i386/testthat.dll
[00:02:26] Error: loading failed
[00:02:26] Execution halted
[00:02:26] *** arch - x64
[00:02:26] ERROR: loading failed for 'i386'
[00:02:26] * removing 'c:/RLibrary/testthat'
[00:02:26] * restoring previous 'c:/RLibrary/testthat'
[00:02:26] Warning in file.copy(lp, dirname(pkgdir), recursive = TRUE, copy.date = TRUE) :
[00:02:26]   problem copying c:\RLibrary\00LOCK-testthat\testthat\libs\i386\testthat.dll to c:\RLibrary\testthat\libs\i386\testthat.dll: Permission denied
[00:02:26] Warning message:
[00:02:26] In i.p(...) :
[00:02:26]   installation of package 'C:/Users/appveyor/AppData/Local/Temp/1/RtmpIx25hi/remotes5743d4a9b1/testthat' had non-zero exit status
```

See https://ci.appveyor.com/project/ApacheSoftwareFoundation/spark/builds/25818746

Our SparkR testbed requires `testthat` 1.0.2 at most for the current status and `devtools` was installed at SPARK-22817 to pin the `testthat` version to 1.0.2

Therefore, this PR works around the current issue by directly installing from the archive instead, and don't use `devtools`.

```R
 R -e "install.packages('https://cloud.r-project.org/src/contrib/Archive/testthat/testthat_1.0.2.tar.gz', repos=NULL, type='source')"
```

## How was this patch tested?

AppVeyor will test.

Closes #25081 from HyukjinKwon/SPARK-28309.

Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

appveyor.yml

@@ -42,9 +42,12 @@ install:
   # Install maven and dependencies
   - ps: .\dev\appveyor-install-dependencies.ps1
   # Required package for R unit tests
-  - cmd: R -e "install.packages(c('knitr', 'rmarkdown', 'devtools', 'e1071', 'survival'), repos='https://cloud.r-project.org/')"
+  - cmd: R -e "install.packages(c('knitr', 'rmarkdown', 'e1071', 'survival'), repos='https://cloud.r-project.org/')"
   # Here, we use the fixed version of testthat. For more details, please see SPARK-22817.
-  - cmd: R -e "devtools::install_version('testthat', version = '1.0.2', repos='https://cloud.r-project.org/')"
+  # As of devtools 2.1.0, it requires testthat higher then 2.1.1 as a dependency. SparkR test requires testthat 1.0.2.
+  # Therefore, we don't use devtools but installs it directly from the archive including its dependencies.
+  - cmd: R -e "install.packages(c('crayon', 'praise', 'R6'), repos='https://cloud.r-project.org/')"
+  - cmd: R -e "install.packages('https://cloud.r-project.org/src/contrib/Archive/testthat/testthat_1.0.2.tar.gz', repos=NULL, type='source')"
   - cmd: R -e "packageVersion('knitr'); packageVersion('rmarkdown'); packageVersion('testthat'); packageVersion('e1071'); packageVersion('survival')"
 
 build_script: