zapcore: recover panics from ObjectMarshaler and ArrayMarshaler (#1504)

[rodionsteshenko]

Fixes #1504

Problem

Panics in user-provided MarshalLogObject and MarshalLogArray implementations crash the entire application. This is inconsistent with the existing panic recovery for Stringer (encodeStringer) and Error types, which gracefully convert panics to PANIC=<msg> error entries.

Fix

Added three panic-recovering wrapper functions (encodeObject, encodeArray, encodeInlinedObject) that mirror the existing encodeStringer pattern. These wrap the calls to enc.AddObject, enc.AddArray, and obj.MarshalLogObject respectively, converting any panic to a PANIC=<msg> error that gets logged as a <key>Error field.

Affected field types:

• ObjectMarshalerType
• ArrayMarshalerType
• InlineMarshalerType

Test

Added panickyObject and panickyArray test types plus 3 new test cases to TestFieldAddingError that verify:

• A panicking ObjectMarshaler does not crash, produces PANIC=panic in MarshalLogObject
• A panicking ArrayMarshaler does not crash, produces PANIC=panic in MarshalLogArray
• A panicking inlined ObjectMarshaler does not crash, produces PANIC=panic in MarshalLogObject

Full test suite passes on macOS ARM (Apple Silicon).

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