Fix tests failing due to directory conflicts

[ace-n-msft]

Problem

When running npx run jasmine on the main branch, I receive several instances of the following error:

DELETE ERROR Error: EBUSY: resource busy or locked, rmdir '\\?\C:\Users\a\Desktop\PowerBI-visuals-tools\spec\.tmp\visualname'
    at rmdirSync (node:fs:1222:10)
    at _rmdirSync (node:internal/fs/rimraf:235:5)
    at rimrafSync (node:internal/fs/rimraf:193:7)
    at node:internal/fs/rimraf:253:9
    at Array.forEach (<anonymous>)
    at _rmdirSync (node:internal/fs/rimraf:250:7)
    at rimrafSync (node:internal/fs/rimraf:193:7)
    at Object.rmSync (node:fs:1271:10)
    at Object.removeSync (C:\Users\a\Desktop\PowerBI-visuals-tools\node_modules\fs-extra\lib\remove\index.js:11:6)
    at FileSystem.deleteTempDirectory (file:///C:/Users/a/Desktop/PowerBI-visuals-tools/spec/helpers/FileSystem.js:103:16) {
  errno: -4082,
  syscall: 'rmdir',
  code: 'EBUSY',
  path: '\\\\?\\C:\\Users\\a\\Desktop\\PowerBI-visuals-tools\\spec\\.tmp\\visualname'
}

From my investigation, this seems to be happening due to multiple [conflicting] concurrent file-write operations on the test's temporary directory.

Proposed Solution

To resolve this, I assigned each test its own unique subdirectory within the temporary directory.

I confirmed this resolution worked by running npx jasmine and verifying that the tests passed without issue.

[ace-n-msft]

(Note: the force-pushes were necessary to get these commits signed by Git. No code changes occurred post-approval.)