Removed underscores from test method names to be consistent with other components.

It is more common to use fully camel-cased names for test methods. Only some of the test methods are called with underscore notation. To avoid confusion it is better to be consistent.
merged branch jakzal/no-underscored-methods-in-tests-master (PR #6885)

This PR was submitted for the master branch but it was merged into the 2.2 branch instead (closes #6885).

Commits
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c5d15f8 [PropertyAccess] Removed underscores from test method names to be consistent with other components.

Discussion
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[PropertyAccess] Removed underscores from test method names

Removed underscores from test method names to be consistent with other components.

This was previously done in #6695, but was partly lost when merging with master (PropertyAccess component was created, so the location of tests has changed).

| Q              | A                                        |
|--------------|--------------------------------|
| Bug fix?          | no |
|New feature? | no |
|BC breaks?    | no |
|Deprecations? |	no |
|Tests pass? | yes |
|Fixed tickets | n/a |
|License | MIT |
|Doc PR | n/a |