tv-casting-app: Handle uncaught exceptions before JNI crashes app and make iOS discoverCommissioners API callback based

[sharadb-amazon]

Fixes #24895 and #24894

Problems fixed

1. If one of the handlers in the tv-casting app for android, throws an exception that it does not handle, it leads to the exception being passed to JNI which crashes the application. This can be tested y temporarily adding a throw new RuntimeException(dummy exc) call in one of the handlers.
2. In the darwin tv-casting-app, the discoverCommissioners API call must be followed by a getDiscoveredCommissioners call after a certain period of time. This is not ideal because the wait time is non-deterministic and leads to the implementation of polling behaviour on the client side. Change the API to be callback based so that the client is called whenever a new commissioner is discovered.

Testing

Tested with the android and iOS tv-casting-apps

[github-actions]

PR #24896: Size comparison from eaa7476 to eb71bf7

Decreases (1 build for cc32xx)

platform	target	config	section	eaa74766	eb71bf7	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	19915393	19915392	-1	-0.0

Full report (1 build for cc32xx)

platform	target	config	section	eaa74766	eb71bf7	change	% change
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			.text	532332	532332	0	0.0

[github-actions]

PR #24896: Size comparison from eaa7476 to 9602c19

Full report (1 build for cc32xx)

platform	target	config	section	eaa74766	9602c19	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	639725	639725	0	0.0
			(read/write)	204084	204084	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197488	197488	0	0.0
			.comment	194	194	0	0.0
			.data	1476	1476	0	0.0
			.debug_abbrev	928401	928401	0	0.0
			.debug_aranges	87336	87336	0	0.0
			.debug_frame	299792	299792	0	0.0
			.debug_info	19915393	19915393	0	0.0
			.debug_line	2646819	2646819	0	0.0
			.debug_loc	2781044	2781044	0	0.0
			.debug_ranges	280656	280656	0	0.0
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			.resetVecs	64	64	0	0.0
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