compute: Add spec support for disabling LFC resizing

[sharnoff]

ref neondatabase/cloud#21731

Problem

When we manually override the LFC size for particular computes, autoscaling will typically undo that because vm-monitor will resize LFC itself.

So, we'd like a way to make vm-monitor not set LFC size — this actually already exists, if we just don't give vm-monitor a postgres connection string.

Summary of changes

Add a new field to the compute spec, disable_lfc_resizing. When set to true, we pass in None for its postgres connection string. That matches the configuration tested in neondatabase/autoscaling CI.

[github-actions]

7121 tests run: 6824 passed, 0 failed, 297 skipped (full report)

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Flaky tests (4)

Postgres 17

• test_idle_checkpoints: debug-x86-64
• test_storage_controller_node_deletion[True]: release-x86-64
• test_create_churn_during_restart: debug-x86-64

Postgres 14

• test_pgdata_import_smoke[None-1024-RelBlockSize.MULTIPLE_RELATION_SEGMENTS]: release-arm64

Code coverage* (full report)

• functions: 31.4% (8401 of 26732 functions)
• lines: 48.1% (66630 of 138656 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
0229962 at 2024-12-13T02:14:54.544Z :recycle:}