statistics: introduce sampling by rate

[winoros]

What problem does this PR solve?

Issue Number: close #27187, close #26547, for #27357

Problem Summary:

Introduce the sampling by rate by implementing the traditional bernoulli sampling tech.

What is changed and how it works?

Proposal: To be added

What's Changed:

Modify the parser in pingcap/parser#1314 to support the new analyze option.
Modify the tipb in pingcap/tipb#236 to support passing sampling rate to tikv.

We implement the Bernoulli sampling in a very simple way

for each element:
	if the rng > sample_rate:
		continue
	add the current row into the samples.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Support collecting samples by sampling rate for ANALYZE OPTION

[ti-chi-bot]

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[winoros]

Note that this pr would be split into small ones for review.
This pr contains all changes when we're doing experiments.

[ti-chi-bot]

@winoros: PR needs rebase.

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