ST6RI-944 Invalidate TypeAdapter#getFeatureMembership cache when needed

[AxelRICHARD]

This PR fixes a bug such that, after an initial call to getFeatureMembership on a Type element, if additional FeatureMemberships are added, they were not being reflected in subsequent calls to getFeatureMembership.

Background

PR #749 (ST6RI-925) introduced caching in TypeAdapter for featureMemberships. This caching happens on the first call to getFeatureMembership. After this, unless the cache is cleared, getFeatureMemberships always returns the cached value, even if new FeatureMembership relationships have been added to the source element.

The following methods directly or indirectly use getFeatureMembership and,so, also reflect this bug:

• Type.getFeature, getDirectedFeature, getEndFeature, getInput, getOutput
• InstantiationExpression.getArgument
• ConnectionDefinition.getConnectionEnd
• InterfaceDefinition.getInterfaceEnd

Note. Association.getAssociationEnd, Connector.getConnectorEnd and FlowDefinition.getFlowEnd and FlowUsage.getConnectorEnd have the same functionality as getEndFeature.

Changes

For each of the methods above, define a corresponding static utility method. The original property methods are re-implemented to first call ElementUtil.clearCache on the method argument, then call the corresponding utility method. Internally, the utility methods are used directly to allow caching to improve performance.

Property Getter Method	Utility Method
Type.getFeatureMembership	TypeUtil.getFeatureMembershipOf
Type.getFeature	TypeUtil.getFeatureOf
Type.getDirectedFeature	TypeUtil.getDirectedFeatureOf
Type.getEndFeature	TypeUtil.getEndFeatureOf
Type.getInput	TypeUtil.getInputOf
Type.getOutput	TypeUtil.getOutputOf
InstantiationExpression.getArgument	ExpressionUtil.getArgumentOf
ConnectionDefinition.getConnectionEnd	UsageUtil.getConnectionEndOf
InterfaceDefinition.getInterfaceEnd	UsageUtil.getInterfaceEndOf

With this approach, performance (as measured using SysMLInteractiveProfiler) is essentially the same as before the changes in this PR. Without caching, there is a performance degradation of 10 to 20%.

[AxelRICHARD]

Hello @seidewitz do you need something else for this pull request? If no, can I set it as "Ready for review"?