Spring-ai refactor(core): extract common function callback builder functionality

Extracts shared function callback builder functionality into DefaultCommonInvokingSpec base class, reducing code duplication across builder implementations. Makes FunctionInvokingSpec and MethodInvokingSpec extend CommonInvokingSpec for better code organization. Also fixes function/description builder order in Anthropic tests.

• Introduced a common base class for function callback builders to centralize shared logic
• Standardized the order of method chaining for function and description in multiple AI model test classes
• Refactored test cases across various AI model integrations
• Corrected builder method order from .description().function() to .function().description() and .description().method() to .method().description()
• Updated multiple test files to consistently use .function() before .description()
• Updated documentation examples to reflect new builder method order
• Modified DefaultFunctionCallbackResolver to maintain new builder method order
• Updated DefaultChatClient and ChatClient test classes to reflect new builder pattern

Comment From: ilayaperumalg

LGTM, need to fix some of the latest changes after rebase. will fix and merge.

Comment From: ilayaperumalg

Rebased, updated minor changes javadoc, fix on PerplexityWithOpenAiChatModelIT and merged as 6a195ee9