stdlib: cache environment variables

[dirkdev98]

Removes the 'log' export from 'insight'.

Accessing process.env.XXX is relatively slow in Node.js.
Benchmark of a plain object property access and accessing process.env.NODE_ENV:

property access       500000000  iterations     0  ns/op
process.env access      5000000  iterations   246  ns/op

See this thread nodejs/node#3104 for some more context

[github-actions]

==== Benchmark result ====

Node.js version: 14

Total benchmarks: 9
          Passed: 9
          Failed: 0
-----------
object validator simple      5000000  iterations     444  ns/op
object validator nested        50000  iterations   41295  ns/op
logger - strings              500000  iterations    2053  ns/op
logger - objects              500000  iterations    2565  ns/op
logger - deep objects         500000  iterations    4447  ns/op
uuid                         2000000  iterations     518  ns/op
uuid.isValid                10000000  iterations     124  ns/op
isNil                      500000000  iterations       0  ns/op
isPlainObject              100000000  iterations      16  ns/op

[github-actions]

==== C8 test coverage ====
Statements: 71.78% ( 17662/24607 )
Branches : 71.32% ( 2091 /2932 )
Functions : 72.44% ( 665 /918 )
Lines : 71.78% ( 17662 /24607 )

[github-actions]

==== Benchmark result ====

Node.js version: 15

Total benchmarks: 9
          Passed: 9
          Failed: 0
-----------
object validator simple      5000000  iterations     480  ns/op
object validator nested        50000  iterations   47916  ns/op
logger - strings              500000  iterations    2167  ns/op
logger - objects              500000  iterations    2816  ns/op
logger - deep objects         500000  iterations    4668  ns/op
uuid                         2000000  iterations     631  ns/op
uuid.isValid                10000000  iterations     143  ns/op
isNil                      500000000  iterations       0  ns/op
isPlainObject              100000000  iterations      17  ns/op