Rollback back-end *node* engine support to LTS

[Martii]

• Keeping applicable TLS restricted for eventual 12.x+ compatibility
• Search query (modelQuery) on, at the very least, about field causes maximum CPU usage in node@12.0.0 through node@12.5.0 but not v11.x or v10.x. This causes severe lag for everyone up to observed sustained 20+ seconds on queries.
• Restarting and exposing with transforming to secondary indexing for Script model as per all mongoose/MongoDB documentation. Use syncIndexes to maintain DB indexes.
• Squash new deprecation warning for MongoDB/*mongoose* deprecations #1516

NOTES:

• This is going to be a major issue when v10.x is EOL'd if node and related dep issues (mongoose, mongodb) aren't resolved
• For some reason mongoose is emitting the index event twice when used globally... unknown reason atm. Picking local disable in favor.

Applies to #1548 and post #1603 with observed issue since then.

Refs:

• https://mongoosejs.com/docs/guide.html#indexes

Dev startup:

$ node app.js
Starting application...
Disabling GitHub `hooks` in unsecure mode
S3rver initialized
error: Error creating bucket. Bucket "openuserjs.org" already exists
info: PUT /openuserjs.org 409 11ms -
Default dev S3 bucket already exists
MongoDB connection is opened
Connected to MongoDB v3.6.12
GitHub client authenticated
Index event triggered/trapped for Script model
Script indexes:
 [ { v: 2,
    key: { _id: 1 },
    name: '_id_',
    ns: 'openuserjs_devel.scripts' },
  { v: 2,
    key: { _authorId: 1, flagged: 1, isLib: 1 },
    name: '_authorId_1_flagged_1_isLib_1',
    ns: 'openuserjs_devel.scripts',
    background: true },
  { v: 2,
    key: { installName: 1 },
    name: 'installName_1',
    ns: 'openuserjs_devel.scripts',
    background: true },
  { v: 2,
    key: { isLib: 1, author: 1, name: 1 },
    name: 'isLib_1_author_1_name_1',
    ns: 'openuserjs_devel.scripts',
    background: true } ]

Recent db stats:

> db.scripts.aggregate( [ { $indexStats: { } } ] );
{ "name" : "_id_", "key" : { "_id" : 1 }, "host" : "<db>:<port>", "accesses" : { "ops" : NumberLong(12842), "since" : ISODate("2019-06-27T04:10:25.453Z") } }
{ "name" : "isLib_1_author_1_name_1", "key" : { "isLib" : 1, "author" : 1, "name" : 1 }, "host" : "<db>:<port>", "accesses" : { "ops" : NumberLong(7348), "since" : ISODate("2019-06-27T12:26:13.574Z") } }
{ "name" : "installName_1", "key" : { "installName" : 1 }, "host" : "<db>:<port>", "accesses" : { "ops" : NumberLong(144052), "since" : ISODate("2019-06-27T04:10:25.453Z") } }
{ "name" : "_authorId_1_flagged_1_isLib_1", "key" : { "_authorId" : 1, "flagged" : 1, "isLib" : 1 }, "host" : "<db>:<port>", "accesses" : { "ops" : NumberLong(16691), "since" : ISODate("2019-06-27T04:10:25.453Z") } }

[Martii]

Guhhh still present with multiple queries outside of myself... ughh... plan B