LSP4iJ: Develop automated UI tests for case insensitive matching of completion items.

[mrglavas]

In a recent PR delivered in LSP4iJ: redhat-developer/lsp4ij#511 matching of completion items is now case insensitive. We should expand our testing, particularly for server.env and bootstrap.properties to cover scenarios with mixed casing and ensure the filtering is working correctly with case insensitive matching of completion items.

See discussion here: #897 for more background information.

Current Scenarios we have right now:

• Full capital case letters insert into server.env
• Full lowercase letters insert into bootstrap.properties

Planned Scenarios to Add Tests as part of this issue fix:

• Full lowercase letters insert into server.env
• A mix of lowercase and capital case letters insert into server.env
• Full capital case letters insert into bootstrap.properties
• A mix of lowercase and capital case letters insert into bootstrap.properties