Python: Handlebars template support

[eavanvalkenburg]

Motivation and Context

Introducing Handlebars templating to the Python Semantic Kernel!

Closes: #5446
Prework for: #4641

Description

Adds HandlebarsPromptTemplate as a subclass of PromptTemplateBase
Adds second literal to the PromptTemplateConfig definition
Adds helpers for Handlebars (system_helpers) and create_helper_from_function function
Moves fully_qualified_name into KernelFunctionMetadata instead of in different extensions.
Defaults are still 'semantic-kernel' templates, and without making explicit changes that still is the norm.
Adds a azure_chat_gpt_handlebars.py sample

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python 3.8 Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel
kernel.py	323	30	91%	190–194, 196–200, 202–206, 214–216, 235, 241, 243–247, 249–253, 255–260, 262, 307–311, 328–333, 340, 344–348, 361, 472, 616
semantic_kernel/connectors/ai/open_ai
utils.py	47	36	23%	27–28, 51–55, 62–63, 104, 137–165
semantic_kernel/functions
kernel_function.py	57	2	96%	119, 138
kernel_function_from_prompt.py	125	3	98%	164, 192, 291
semantic_kernel/planners
planner_extensions.py	36	16	56%	20–29, 33, 37–38, 51–58, 66–77
semantic_kernel/planners/sequential_planner
sequential_planner.py	65	5	92%	71, 75, 106, 122, 130
sequential_planner_extensions.py	55	9	84%	35–36, 57, 108–126
sequential_planner_parser.py	77	12	84%	63–72, 92, 115–118
semantic_kernel/planners/stepwise_planner
stepwise_planner.py	225	141	37%	12, 95, 109–127, 136–206, 227–230, 238–249, 252, 260–275, 278–314, 317–345, 348–353, 356–368, 371–374, 387–399, 402
semantic_kernel/prompt_template
kernel_prompt_template.py	80	3	96%	112–114
prompt_template_config.py	51	5	90%	47, 68, 73–74, 82
TOTAL	5064	1004	80%

Python 3.8 Unit Test Overview

Tests	Skipped	Failures	Errors	Time
1060	11 💤	0 ❌	0 🔥	21.217s ⏱️

[moonbox3]

Looking great

[juliomenendez]

Looks good, besides @moonbox3 comments I didn't see anything else to change.

[moonbox3]

Awesome work.