EAM API: remove appid from appinstance path

[gainsley]

What type of PR is this?

• enhancement/feature

What this PR does / why we need it:

Removes appId from the appinstances path. For retrieval, it becomes an optional parameter, allowing a single API call to get appinstances from different Apps. For delete, it is not necessary because appInstanceId is sufficient to identify the instance.

Which issue(s) this PR fixes:

Fixes #299

Special notes for reviewers:

Changelog input

 release-note

Additional documentation

docs

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ ACTION	actionlint	2		0	0.02s
✅ JSON	eslint-plugin-jsonc	1	0	0	1.43s
✅ JSON	jsonlint	1		0	0.18s
✅ JSON	prettier	1	1	0	0.93s
✅ JSON	v8r	1		0	2.14s
✅ OPENAPI	spectral	3		0	6.02s
✅ REPOSITORY	git_diff	yes		no	0.57s
✅ REPOSITORY	secretlint	yes		no	4.65s
✅ YAML	yamllint	3		0	0.8s

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