Add Python interview questions 151-155

[ahmadalwareh]

Summary

Extends the "150+ Python Interview Questions" reference (readme.md) with five
new advanced questions (151–155) that "go deeper" into CPython internals and
modern concurrency — continuing the threads already running through the document.

What changed

• Added 5 entries to the Table of Contents (with correct GitHub heading anchors).
• Added 5 full question + answer sections at the end of the file.
• Docs-only change: no code, config, or dependencies touched.

New questions

#	Topic	Builds on
151	Free-threaded Python (PEP 703, no-GIL) & subinterpreters (PEP 684/734)	GIL: Q1, Q2, Q23, Q119
152	Bytecode execution: dis, ceval loop, frames, PEP 659 specializing interpreter	Q85, Q86
153	CPython memory: pymalloc arenas/pools/blocks, tracemalloc, leaks & fragmentation	Q11, Q90, Q115, Q135
154	Generators as coroutines (send/throw/close, yield from) → async/await	Q36, Q37, Q118
155	Class customization without a metaclass: __init_subclass__, __set_name__, descriptors	Q46, Q120, Q134

Style & consistency

• Matches the existing format: bold key terms, cross-references to earlier questions,
  one illustrative code block per answer, and a closing takeaway.
• ToC anchors verified against the GitHub slug format used throughout the file.
• The # 150+ Python Interview Questions title already covers the higher count — no change needed.

Notes

• Each answer ties back to this repo where relevant (FastAPI event loop, Celery workers,
  long-running-worker memory diagnosis) to keep it grounded in the codebase.

How to verify

• Open readme.md, confirm ToC entries 151–155 link to their sections.
• readme.md grows from 5777 → 5939 lines; no other files changed.